CN114142167B - Diaphragm and lithium ion battery containing same - Google Patents
Diaphragm and lithium ion battery containing same Download PDFInfo
- Publication number
- CN114142167B CN114142167B CN202111442846.7A CN202111442846A CN114142167B CN 114142167 B CN114142167 B CN 114142167B CN 202111442846 A CN202111442846 A CN 202111442846A CN 114142167 B CN114142167 B CN 114142167B
- Authority
- CN
- China
- Prior art keywords
- membrane
- additive
- separator
- coating
- diaphragm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a diaphragm and a lithium ion battery containing the diaphragm, wherein the diaphragm comprises a diaphragm coating; the diaphragm coating contains a first additive and a second additive, and the mass ratio (g; g) of the first additive to the second additive is 2:8-8:2; the diaphragm coating comprises a plurality of glue layer holes, and the aperture of each glue layer hole is 0.01-10 mu m. According to the invention, through reducing the electrostatic adsorption capacity of the surface of the oil system/oil system mixed coating diaphragm, tiny particles can be reduced, the self-discharge value of the battery cell is reduced, and the quality of the battery cell is improved.
Description
Technical Field
The invention belongs to the technical field of diaphragms, and particularly relates to a diaphragm and a lithium ion battery containing the diaphragm.
Background
The currently used separator is a porous polyolefin product (e.g., three layers of PE, PP/PE/PP), and one or both sides of the substrate separator are coated with inorganic particles (e.g., alumina, boehmite, magnesia, magnesium hydroxide, etc.), and on the basis of this, a pure glue or a mixed coating of glue and ceramic particles (the glue may be a single kind of PVDF or a mixed product of multiple kinds of PVDF) is applied on one or both sides, and aqueous coating and oil coating may be used as the coating.
The aqueous separator means: dispersing single or multiple PVDF in water, grinding to form suspension, filtering, and coating by micro gravure roll transfer coating or spraying. The oil-based separator means: and (3) dissolving single or multiple PVDF in a certain proportion (m: n, m and n can be 0-10) in an organic solvent (such as NMP, DMAC/acetone and the like) to obtain a finished product, wherein the coating mode can be micro gravure roll transfer coating or direct dip coating.
Under different processing modes, the surface static values of the diaphragm are different, for example, the static value of a water-based diaphragm is less than 300V, the static value of a single-sided ceramic double-sided oil system product is about 1000V, and the static of a double-sided ceramic and adhesive mixed coating diaphragm is as high as more than 3000V or more. The diaphragm is often provided with larger static electricity in the process of preparing the lithium ion battery, and can adsorb tiny particles in the air, so that the inside of a battery core of the lithium ion battery is in a micro short circuit state (for example, the voltage drop of the battery core is very obvious, and the maximum value can reach 0.1mV/h or more).
Disclosure of Invention
According to the invention, the additive is introduced into the diaphragm, so that a structure with a low static function is formed on the surface of the diaphragm, the static value of the diaphragm is reduced, and the low static and high process capability can be realized on the premise of not reducing the adhesiveness between the diaphragm and the electrode plate, for example, the yield of the battery is higher, and the core pulling rate of the poor item and the Hi-post poor occupation ratio are lower.
The invention provides the following technical scheme:
a separator comprising a separator coating; the diaphragm coating contains a first additive and a second additive, and the mass ratio (g; g) of the first additive to the second additive is 2:8-8:2; the diaphragm coating comprises a plurality of glue layer holes, and the aperture of each glue layer hole is 0.01-10 mu m.
According to the invention, in the glue layer holes, the glue layer holes with the aperture of 1-3 μm account for 30-70% of the total number of the glue layer holes.
According to the invention, the second additive is an organic microsphere, and the organic microsphere meets at least one of the following conditions:
1) The weight average molecular weight of the organic matters in the organic matter microsphere is 5 multiplied by 10 5 ～30×10 5 ；
2) The average particle diameter D50 of the organic matter microsphere is 0.1-300 mu m;
3) The melting point of the organic matters in the organic matter microspheres is 100-200 ℃;
4) The organic matters in the organic matter microsphere are selected from at least one of fluorine-containing polymers or acrylic polymers;
5) The organic microspheres are partially dissolved or rarely dissolved into an organic solvent, so that the mesh structure is formed;
6) The organic matters in the organic matter microsphere are selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polymethyl methacrylate (PMMA).
According to the invention, the first additive is connected to the surface of the second additive in a long chain network.
According to the invention, the first additive is selected from PVDF, with a melting point of 150-160℃and a weight average molecular weight of 3X 10 5 ～7×10 5 。
According to the present invention, the separator includes a substrate separator and the separator coating layer on at least one surface of the substrate separator, the separator coating layer having a thickness of 0.1 μm to 3 μm.
According to the present invention, when the separator coating layers are provided on both surfaces of the substrate separator, the separator includes 2 separator coating layers, and the total thickness of the 2 separator coating layers is 0.2 μm to 5 μm.
According to the invention, the thickness of the substrate membrane is 1 μm to 30 μm.
According to the invention, the substrate separator is selected from a single-layer substrate separator or a multi-layer substrate separator composed of PE and/or PP.
According to the invention, the membrane is an oil-based membrane.
According to the invention, the membrane has an average electrostatic value of less than 1500V.
According to the invention, the self-discharge mean value of the diaphragm is less than 0.045mV/h.
The invention also provides a lithium ion battery, which comprises the diaphragm.
The beneficial effects are that:
according to the invention, the second additive organic matter is introduced to the surface of the diaphragm, so that the organic matter and the first additive are partially crosslinked in a solvent system, and meanwhile, most of the second additive organic matter keeps the original complete form, can form a ball-linking phenomenon with the first additive, and the balls can be connected on the surfaces of different balls, so that a multi-layer bee-shaped structure can be formed, and a large giant mesh structure can be formed, so that the electrostatic value of the oil-based diaphragm or the oil-based mixed-coating diaphragm is obviously reduced, for example, from 3000V or higher to less than 1200V. According to the invention, through reducing the electrostatic adsorption capacity of the surface of the oil system/oil system mixed coating diaphragm, tiny particles can be reduced, the self-discharge value of the battery cell is reduced, and the quality of the battery cell is improved.
According to the invention, the organic microspheres with the second additive and the first additive are introduced into the surface of the diaphragm to form a mesh structure, so that the diaphragm can be used for replacing ceramic particles introduced into the diaphragm coating at present, and the purposes of reducing the surface energy of the diaphragm surface coating and reducing the static electricity on the diaphragm surface are achieved.
Drawings
FIG. 1 is a schematic illustration of the organics of the present invention in a coating; wherein the black spheres represent the first additive organic matter; the lines represent the second additive of the separator surface coating;
FIG. 2 is an SEM image of the surface of a separator of example 1;
FIG. 3 is an SEM image of the surface of a separator of example 2;
FIG. 4 is an SEM image of the surface of a separator of example 3;
FIG. 5 is an SEM image of the surface of a separator of example 4;
FIG. 6 is an SEM image of the surface of a separator of comparative example 1;
FIG. 7 is a schematic illustration of core pulling; wherein 1-winding core; 2-electrode lugs; 3-separator.
Detailed Description
As previously described, the present invention provides a separator coating comprising a first additive and a second additive; the diaphragm coating comprises a plurality of glue layer holes, and the aperture of each glue layer hole is 0.01-10 mu m.
According to an embodiment of the invention, the first additive and the second additive form a multi-angle interconnected network structure in the separator coating, the network structure comprising the plurality of glue line holes. In particular, as shown in fig. 2 or 3.
According to the embodiment of the invention, in the glue layer holes, the glue layer holes with the aperture of 1-3 μm account for 30-70% of the total number of the glue layer holes. Such pore size, in particular such pore size distribution, is selected because such pore size distribution can form lamellar and porous distribution, can increase the specific surface area of the oil-based diaphragm, thus reduce the static electricity generation of the diaphragm in the coating, slitting and using processes, and is favorable for the diaphragm to be used; for example, when the pore size of the glue layer is <1 μm high (e.g., up to 40% or more), the electrostatic value of the separator is significantly higher (> 2000V), which is disadvantageous for production. In addition, if the pore diameters are all the same, the adhesive force between the adhesive layer and the pole piece becomes weak, so that the range of 30% -70% is selected.
According to an embodiment of the present invention, the second additive is an organic microsphere, and the weight average molecular weight of the organic matters in the organic microsphere is 5×10 5 ～30×10 5 . Specifically, the weight average molecular weight thereof is 8×10 5 ～10×10 5 Or 10X 10 5 ～30×10 5 The method comprises the steps of carrying out a first treatment on the surface of the For example, it may be 5×10 5 、6×10 5 、7×10 5 、8×10 5 、8.5×10 5 、9×10 5 、10×10 5 、11×10 5 、12×10 5 、13×10 5 、14×10 5 、15×10 5 、20×10 5 、30×10 5 . The inventor finds that the larger the molecular weight of the organic matters in the organic matter microsphere is, the larger the polarity is, the longer the molecular chain is, the longer the organic matters are dissolved in the organic solvent, the more favorable the mesh structure is formed, and the more obvious the layered structure of the structure is, the more obvious the antistatic effect is.
According to an embodiment of the present invention, the organic microspheres have an average particle diameter D50 of 0.1 μm to 300 μm. The organic microspheres have an average particle size D50 of, for example, 0.3 μm to 10. Mu.m, in particular 0.3 μm to 5. Mu.m, for example, 0.1 μm, 0.3 μm, 1 μm, 2 μm, 3 μm, 3.5 μm, 3.724 μm, 4 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm or 300. Mu.m. The microspheres having such a particle size distribution are selected so that the smaller the average particle size D50 of the organic microspheres is, the more uniform the mesh structure is formed, and the smaller the average particle size D50 is, which is advantageous in coating control.
According to an embodiment of the invention, the melting point of the organic matters in the organic matter microsphere is 100-200 ℃; illustratively, the melting point is 140 ℃ to 155 ℃; specifically, the melting point may be 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, or 200 ℃. When the melting point of the organic matters is too low, the glass transition temperature of the organic matters is low, which is not beneficial to the application of the diaphragm; when the melting point of the organic matter is too high, the crystallinity of the organic matter is too high, which is unfavorable for forming a mesh structure.
According to an embodiment of the present invention, the organic matters in the organic matter microsphere is selected from at least one of fluorine-containing polymer or acrylic polymer, and the organic matter microsphere is partially dissolved or very little partially dissolved into an organic solvent (such as NMP or DMAC) to form a foundation of the above-mentioned mesh structure, and the above-mentioned mesh structure is further formed by interconnection of the first additive.
According to an embodiment of the present invention, the organic matter in the organic matter microsphere is selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or polymethyl methacrylate (PMMA).
Illustratively, the organic matter in the organic matter microsphere is selected from PVDF, which has properties of the organic matter, such as weight average molecular weight and melting point, as described above.
According to an embodiment of the invention, the first additive is selected from the group consisting of organics comprising organics in the organic microspheres of the second additive; the first additive is connected to the surface of the second additive (e.g., organic microspheres) in a long chain network, thereby forming the network structure.
Illustratively, the first additive is selected from PVDF having a melting point of 150 to 160℃and a weight average molecular weight of 3X 10 5 ～7×10 5 。
According to embodiments of the present invention, the mass ratio (g: g) of the first additive to the second additive is 2:8 to 8:2, specifically, the two may be matched according to the solubility or molecular weight, for example, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3 or 8:2. The above mesh structure is obtained by adjusting the mass ratio of the first additive to the second additive. If only the second additive is added, the formation of the above-mentioned mesh structure is not facilitated.
The invention also provides a diaphragm, which comprises the diaphragm coating.
According to an embodiment of the present invention, the separator includes a substrate separator and the above-described separator coating layer provided on at least one surface of the substrate separator.
According to an embodiment of the invention, the membrane comprises 1 membrane coating layer when the membrane coating layer is provided on one surface of the substrate membrane, the thickness of 1 membrane coating layer is 0.1 μm to 3 μm, for example 0.8 μm to 1.2 μm.
According to an embodiment of the invention, the membrane comprises 2 membrane coatings when the membrane coatings are provided on both surfaces of the substrate membrane, the total thickness of the 2 membrane coatings being between 0.2 μm and 5 μm, for example between 1.8 μm and 2.2 μm.
According to an embodiment of the invention, the substrate separator is selected from a single-layer substrate separator or a multi-layer substrate separator consisting of PE and/or PP. Illustratively, the substrate separator is selected from the group consisting of PP/PE/PP three-layer substrate separators.
According to an embodiment of the present invention, the second additive forms a stable skeletal support in the membrane coating (as shown in fig. 1), which is capable of protruding the membrane coating on the membrane surface, thereby forming glue line holes on the membrane coating surface, which form the mesh structure by interconnection of the first additive, as shown in fig. 2 or 3 in particular.
According to an embodiment of the present invention, the thickness of the substrate separator is 1 μm to 30 μm.
According to an embodiment of the invention, the membrane is an oil-based membrane.
According to an embodiment of the invention, the membrane has an electrostatic value average of less than 1500V. The inventor finds that when the average value of the electrostatic value of the diaphragm is smaller than 1500V, the capability of the diaphragm for adsorbing tiny particles in the air is reduced, so that the probability of the diaphragm for adsorbing tiny particles and further foreign matters introduced into the battery cell body can be reduced.
According to an embodiment of the invention, the self-discharge mean value of the separator is less than 0.045mV/h. The inventor finds that when the self-discharge value diaphragm is applied to the battery cells, the single battery cell has good long-term storage performance, the serial voltage difference of a plurality of battery cells is small, and the failure proportion of the battery cells is reduced.
According to the embodiment of the invention, the diaphragm is not easy to attract light and small objects in the use process, so that the probability of foreign matters entering the battery cell body can be reduced.
The invention also provides a lithium ion battery, which comprises the diaphragm.
According to an embodiment of the invention, the lithium ion battery further comprises a positive electrode.
According to an embodiment of the present invention, the positive electrode includes at least a positive electrode current collector, a positive electrode coating layer, and a tab.
According to an embodiment of the present invention, the positive electrode current collector is selected from aluminum foils having a thickness of 8 to 14 μm.
According to an embodiment of the present invention, the positive electrode coating layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.
According to an embodiment of the invention, the positive electrode active material is selected from LiCoO 2 、LiNiO 2 、LiFePO 4 、LiMn 2 O 4 Or LiNi x Co y Mn 1-x-y O 2 At least one of them.
According to an embodiment of the present invention, the positive electrode conductive agent is selected from at least one of conductive carbon black, carbon nanotubes, conductive graphite, or graphene.
According to an embodiment of the present invention, the positive electrode binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-fluorinated olefin, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber, or polyvinyl alcohol.
According to an embodiment of the present invention, in the positive electrode coating layer, the mass fraction of the positive electrode active material is 96% to 98.5%, the mass fraction of the positive electrode conductive agent is 0.5% to 2.5%, and the mass fraction of the positive electrode binder is 1% to 1.5%.
According to an embodiment of the invention, the lithium ion battery further comprises a negative electrode.
According to an embodiment of the present invention, the negative electrode includes a positive electrode current collector, a negative electrode coating layer, and a tab.
According to an embodiment of the present invention, the anode coating layer includes an anode active material, an anode conductive agent, an anode binder, and a dispersing agent.
According to an embodiment of the present invention, the negative electrode active material is selected from at least one of mesophase carbon microspheres, artificial graphite, natural graphite, hard carbon, soft carbon, lithium titanate, a silicon-based material, a tin-based material, or lithium metal.
According to an embodiment of the present invention, the negative electrode conductive agent is selected from at least one of conductive carbon black, carbon nanotubes, conductive graphite, or graphene.
According to an embodiment of the present invention, the negative electrode binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-fluorinated olefin, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber, polyvinyl alcohol.
According to an embodiment of the invention, the dispersant is selected from sodium carboxymethyl cellulose and/or potassium carboxymethyl cellulose.
According to an embodiment of the present invention, in the anode coating layer, the mass fraction of the anode active material is 95% -97%, the mass fraction of the anode conductive agent is 1.0% -2%, the mass fraction of the anode adhesive is 1% -1.5%, and the mass fraction of the dispersing agent is 0% -1.5%.
The technical scheme of the invention will be further described in detail below with reference to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
Unless otherwise indicated, the starting materials and reagents used in the following examples were either commercially available or may be prepared by known methods.
Abbreviations in the present invention are as follows: DMAC refers to dimethylacetamide; DMF refers to N, N-dimethylformamide.
The second additive used in the following comparative examples and examples was polyvinylidene fluoride (PVDF) microspheres, wherein PVDF had a melting point of 145.+ -. 5 ℃ and a weight average molecular weight of 8X 10 5 ～10×10 5 The average particle diameter D50 of the microspheres was 3.724. Mu.m. The first additive is conventional PVDF with a melting point of 150-160deg.C and a weight average molecular weight of 3×10 5 ～7×10 5 Between them.
The static value in the invention is obtained by the Kernel SK-H050 test.
Example 1
Preparation of oily separator
The PVDF microspheres of the second additive are selected to be added with 10 percent of the weight for coating production, the diaphragm base material is PE, and the thickness is 5 mu m; the solid content of the coating slurry is 7.5%, and the solvent is DMAC; the PVDF accounts for 37.5%, the PVDF as the second additive is added into the coating slurry according to 10% of the total PVDF, stirring is carried out for 30min, the viscosity of the slurry is controlled to be 130-180 mPa.s, the coating is double-sided coating, the total thickness of 2 coatings is 2 mu m, and the oily diaphragm 1 is obtained after the coating.
The above oily separator 2 was subjected to a test, and the surface static electricity value was measured and recorded in table 1.
Example 2
Preparation of oily separator
The preparation method of the separator of this example was the same as that of example 1, except that the second additive PVDF microspheres accounted for 30% of the total mass of PVDF, resulting in an oily separator 2. The surface static values were measured and recorded in table 1.
Example 3
Preparation of oily separator
The preparation method of the separator of this example was the same as that of example 1, except that the second additive PVDF microspheres accounted for 50% of the total mass of PVDF, resulting in an oily separator 3. The surface static values were measured and recorded in table 1.
Example 4
Preparation of oily separator
The preparation method of the separator of this example was the same as that of example 1, except that the second additive PVDF microspheres accounted for 70% of the total mass of PVDF, to obtain an oily separator 4. The surface static values were measured and recorded in table 1.
Comparative example 1
In the coating slurry, the solid content is 7.5%, and the solvent is DMAC; wherein the first additive is conventional PVDF, which accounts for 37.5% of the total mass of the solid, and the viscosity of the solution is 130-180 mPa.s.
The coating slurry was coated on the surface of a PE base separator having a thickness of 5 μm, the coating thickness was double-sided coating, and the total thickness of 2 coating layers was 2 μm, to obtain an oily separator 5 after coating.
The above oily separator 5 was tested and the surface static electricity value was recorded in table 1.
Test example 1
As shown in fig. 2-5, which are SEM images of the membrane surfaces of examples 1-4, it can be seen from the SEM images that the membrane surfaces form a mesh structure as shown in fig. 2-5, that organics, which can be partially swollen or dissolved by high temperature and long time immersion in (an) organic solvent, form a skeleton and a connection between the coating layers, can be attached to PVDF components that have been dissolved in the solvent around the spheres when partial dissolution occurs, forming a unique morphology (such as the skeleton support structure shown in fig. 1) having multiple voids and a specific skeleton structure. The pore size distribution of the separator coating is observed and recorded in table 1 from SEM images of the separator surfaces of fig. 2-5, where pore size refers to the diameter of the pores forming the surface, calculated as the major axis direction when the pores are elliptical.
As shown in fig. 6, which is an SEM image of the separator surface of comparative example 1, it can be seen from the SEM image that the separator surface has no mesh structure, and the pore size distribution of the separator surface is recorded in table 1.
Test example 2
1. And (3) preparation of a soft package battery:
a diaphragm: the separators 1 to 5 prepared in the above comparative example 1 and examples 1 to 4 were selected, respectively;
positive electrode structure: the foil material is selected from aluminum foil,10 μm; the positive electrode coating layer includes: the positive electrode active material is LiCoO 2 The proportion is 97.80%; the conductive agent is conductive carbon black, and accounts for 1.10 percent; the binder is polyvinylidene fluoride, and the proportion is 1.10%;
negative electrode structure: copper foil is selected as the foil material, and the thickness of the foil material is 5 mu m; the negative electrode coating layer includes: the negative electrode active material is mesophase carbon microsphere with a proportion of 96.50%, the conductive agent is carbon nano tube with a proportion of 0.90%, the adhesive is SBR with a proportion of 1.30%, the dispersing agent is sodium carboxymethylcellulose/CMC with a proportion of 1.30%;
electrolyte solution: EC: EMC: dec=3:5:2, lipf6 accounts for 13%;
the separator 1-5 was assembled with the positive electrode and the negative electrode, respectively, to form a soft-pack battery, denoted as battery 1-5.
2. The self-discharge test method of the battery cell comprises the following steps: the batteries 1 to 5 of the above examples 1 to 4 and comparative example 1 were subjected to primary formation activation or capacity screening by taking 32PCS respectively, then aged at 45℃for 48 hours, taken out and left standing at normal temperature for 24 hours, the test cell voltage V1 was recorded as t1, then subjected to secondary voltage test after 48 hours was recorded as V2, and the time was recorded as t2, and then the cell self-discharge magnitude K (unit mV/h) was:
k= (V1-V2)/(t 2-t 1); the average value obtained by calculating the K value of each group of batteries is the self-discharge average value, and the average value is recorded in the table 1.
3. Core pulling detection:
the diaphragms of the above examples 1-4 and comparative example 1 are grouped for use in the production of the battery core winding process, each group is followed by 3000pcs of production, the core pulling phenomenon means that the diaphragm at the innermost ring is in direct contact with the winding needle in the winding process, when the winding needle is pulled out, the diaphragm is pulled out of the winding core due to high electrostatic adsorption or kinetic friction force between the diaphragm and the winding needle, and the core pulling is caused, as shown in fig. 7, wherein a represents the length of the part of the diaphragm exposed out of the winding core, namely a represents the core pulling distance of the winding core, and the unit is millimeter. When a is more than or equal to 0 and less than or equal to 0.5mm, the quality of the spot core is considered to be qualified; when a is more than 0.5mm, the quality of the winding core is considered to be unqualified. Recording the number of unqualified winding cores, and calculating the reject ratio according to the following formula: core pulling failure rate = number of failed cores/3000, and the calculation results are recorded in table 1.
4. Hi-post test:
the batteries 1 to 5 of the above examples 1 to 4 and comparative example 1 were each grouped into 3000PCS and used for the present test, and Hi-post test was performed on an insulation resistance tester (model: HIOKI ST 5520) under the following conditions: voltage 100V, time 2.5s, face pressure: and 0.2Mpa, and is qualified when the resistance value is more than 2MΩ, and is unqualified when the resistance value is less than 2MΩ. Hi-post reject ratio = number of reject cells per group/3000, the calculation results are recorded in table 1.
Table 1 test results
From the test results in table 1, it is clear that the oily separator of comparative example 1 has a large electrostatic value, and is liable to adsorb light and small dust or particles, resulting in a large self-discharge inside the cell. The oily separators of examples 1 to 4 had static values of less than 1200V, and the film surfaces thereof had static values smaller than those of the aqueous separator. From this, it can be seen that after the second additive organic microspheres, a unique crosslinking effect is formed in the coating of the separator, so as to obtain the adhesive layer hole of the adhesive layer of the separator, which is specifically: the aperture of the glue layer hole is 0.01-10 mu m; among the glue layer holes, the glue layer holes with the aperture of 1-3 μm account for 30-70% of the total number of the glue layer holes. Therefore, the diaphragm glue layer can effectively reduce the static value of the diaphragm coating, reduce the capability of absorbing light and small objects/particles on the surface of the diaphragm, achieve the effect of reducing the self-discharge of the battery cell, and form a mesh structure with obvious reduction of the surface static value along with the increase of the content of the organic microspheres of the second additive, and after the diaphragm of the embodiment 1-4 is used for the battery cell, the self-discharge average value of the battery cell is reduced.
The method can reduce the surface static value by adding a certain amount of second additive organic matters to change the surface morphology of the intaglio oil-based diaphragm, and simultaneously increase the manufacturability of the diaphragm.
According to the invention, the organic microspheres with the second additive and the first additive are introduced on the surface of the diaphragm to form a mesh structure, so that the porous ceramic membrane can be used for replacing ceramic particles introduced in the adhesive layer of the diaphragm at present.
The above description of exemplary embodiments of the invention has been provided. However, the scope of protection of the present application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, or the like, which are within the spirit and principles of the present invention, should be made by those skilled in the art, and are intended to be included within the scope of the present invention.
Claims (10)
1. A separator, wherein the separator comprises a separator coating; the diaphragm coating comprises a first additive and a second additive, wherein the first additive is selected from PVDF, the second additive is an organic microsphere, and the mass ratio of the first additive to the second additive is 2:8-8:2; the diaphragm coating comprises a plurality of glue layer holes, wherein the aperture of each glue layer hole is 0.01-10 mu m; the second additive forms a stable framework support in the membrane coating and can protrude the membrane coating on the surface of the membrane so as to form the glue layer holes on the surface of the membrane coating;
among the glue layer holes, the glue layer holes with the aperture of 1-3 μm account for 30-70% of the total number of the glue layer holes.
2. The separator of claim 1, wherein the organic microspheres satisfy at least one of the following conditions:
1) The weight average molecular weight of the organic matters in the organic matter microsphere is 5 multiplied by 10 5 ~30×10 5 ；
2) The average particle diameter D50 of the organic matter microsphere is 0.1-300 mu m;
3) The melting point of the organic matters in the organic matter microspheres is 100-200 ℃;
4) The organic matters in the organic matter microsphere are selected from at least one of fluorine-containing polymers or acrylic polymers;
5) The organic microspheres are partially dissolved or rarely dissolved into the organic solvent, thereby forming a mesh structure.
3. The separator according to claim 2, wherein the organic matter in the organic matter microsphere is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene or polymethyl methacrylate.
4. The separator of claim 1, wherein the first additive is attached to the surface of the second additive in a long chain network;
and/or PVDF has a melting point of 150-160deg.C and a weight average molecular weight of 3×10 5 ~7×10 5 。
5. The membrane of claim 1, wherein the membrane comprises a substrate membrane and the membrane coating on at least one surface of the substrate membrane.
6. The membrane of claim 5, wherein when the glue layer is disposed on one surface of the substrate membrane, the membrane comprises 1 membrane coating, 1 membrane coating having a thickness of 0.1 μm to 3 μm;
when the membrane coating is disposed on both surfaces of the substrate membrane, the membrane comprises 2 membrane coatings, and the total thickness of the 2 membrane coatings is 0.2 μm to 5 μm.
7. The membrane of claim 5, wherein the substrate membrane has a thickness of 1 μm to 30 μm.
8. The separator according to claim 5, wherein the substrate separator is selected from a single-layer substrate separator or a multi-layer substrate separator composed of PE and/or PP.
9. The membrane of any one of claims 1-8, wherein the membrane is an oil-based membrane;
and/or the membrane has an electrostatic value average of less than 1500V;
and/or the self-discharge average value of the diaphragm is less than 0.045mV/h.
10. A lithium ion battery, characterized in that it comprises a separator according to any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111442846.7A CN114142167B (en) | 2021-11-30 | 2021-11-30 | Diaphragm and lithium ion battery containing same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111442846.7A CN114142167B (en) | 2021-11-30 | 2021-11-30 | Diaphragm and lithium ion battery containing same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114142167A CN114142167A (en) | 2022-03-04 |
| CN114142167B true CN114142167B (en) | 2023-05-02 |
Family
ID=80389891
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111442846.7A Active CN114142167B (en) | 2021-11-30 | 2021-11-30 | Diaphragm and lithium ion battery containing same |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114142167B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023078409A1 (en) * | 2021-11-05 | 2023-05-11 | 珠海冠宇电池股份有限公司 | Separator and lithium ion battery comprising same |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020211621A1 (en) * | 2019-04-18 | 2020-10-22 | 比亚迪股份有限公司 | Porous diaphragm and preparation method therefor, and lithium-ion battery |
| CN112038549A (en) * | 2019-09-03 | 2020-12-04 | 李华 | PMMA crosslinked spherical micro powder coating diaphragm and preparation method thereof and application of PMMA crosslinked spherical micro powder coating diaphragm in lithium ion battery |
| WO2021052365A1 (en) * | 2019-09-18 | 2021-03-25 | 珠海冠宇电池股份有限公司 | Ceramic microsphere, separator comprising ceramic microsphere, and lithium ion battery comprising separator |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012100064A1 (en) * | 2011-01-19 | 2012-07-26 | E. I. Du Pont De Nemours And Company | Lithium battery separator with shutdown function |
| CN110120485B (en) * | 2018-02-06 | 2021-06-18 | 比亚迪股份有限公司 | Polymer diaphragm and preparation method and application thereof, and lithium ion battery and preparation method thereof |
| CN113785439B (en) * | 2020-03-27 | 2024-03-26 | 宁德新能源科技有限公司 | Separator, electrode assembly, battery and electronic device |
| CN112018312A (en) * | 2020-09-16 | 2020-12-01 | 珠海冠宇电池股份有限公司 | Diaphragm and battery comprising same |
| CN113644378B (en) * | 2021-08-10 | 2023-05-09 | 深圳市鼎泰祥新能源科技有限公司 | Functional coating diaphragm and preparation method and application thereof |
-
2021
- 2021-11-30 CN CN202111442846.7A patent/CN114142167B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020211621A1 (en) * | 2019-04-18 | 2020-10-22 | 比亚迪股份有限公司 | Porous diaphragm and preparation method therefor, and lithium-ion battery |
| CN112038549A (en) * | 2019-09-03 | 2020-12-04 | 李华 | PMMA crosslinked spherical micro powder coating diaphragm and preparation method thereof and application of PMMA crosslinked spherical micro powder coating diaphragm in lithium ion battery |
| WO2021052365A1 (en) * | 2019-09-18 | 2021-03-25 | 珠海冠宇电池股份有限公司 | Ceramic microsphere, separator comprising ceramic microsphere, and lithium ion battery comprising separator |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114142167A (en) | 2022-03-04 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US20210265702A1 (en) | Composite lithium battery separator and preparation method therefor | |
| CN107316968B (en) | Viscous battery diaphragm and lithium ion battery using same | |
| CN112750976B (en) | Lithium battery core and lithium ion battery | |
| CN111653717B (en) | Preparation method of composite diaphragm, composite diaphragm and lithium ion battery | |
| CN109167012B (en) | Multilayer composite structure diaphragm, preparation method thereof and lithium-sulfur battery | |
| CN112271270B (en) | Lithium ion battery electrode, preparation method thereof and lithium ion battery | |
| KR101179378B1 (en) | Secondary-battery current collector, secondary-battery cathode, secondary-battery anode, secondary battery and production method thereof | |
| CN107431165B (en) | Integrated electrode assembly and electrochemical device including the same | |
| CN113451708A (en) | Functional coating diaphragm and preparation method thereof, lithium ion battery cell, lithium ion battery pack and application thereof | |
| WO2016165633A1 (en) | Polymer composite membrane and preparation method thereof, gel electrolyte and lithium ion battery having the same | |
| KR101357464B1 (en) | Secondary-battery current collector, secondary-battery cathode, secondary-battery anode, secondary battery and production method thereof | |
| CN108807819B (en) | Diaphragm, preparation method thereof and lithium-sulfur battery | |
| US11205822B2 (en) | Non-porous separator and use thereof | |
| US11824225B2 (en) | Separator including substrate, hydrophilic blocking layer, and polar polymer bonding with nodal structure, and method of preparing the same | |
| CN111710832A (en) | Silicon-containing negative plate, preparation method thereof and lithium ion secondary battery manufactured by silicon-containing negative plate | |
| CN112467308A (en) | Diaphragm, preparation method thereof and lithium ion battery | |
| CN108023051B (en) | Isolation film and lithium ion battery containing same | |
| CN114142167B (en) | Diaphragm and lithium ion battery containing same | |
| CN112467309A (en) | Diaphragm and electrochemical device | |
| CN110459732B (en) | Silicon/graphene/carbon composite fiber membrane negative electrode plate, preparation method thereof and lithium ion battery | |
| CN112038549A (en) | PMMA crosslinked spherical micro powder coating diaphragm and preparation method thereof and application of PMMA crosslinked spherical micro powder coating diaphragm in lithium ion battery | |
| CN111916753A (en) | Negative plate and lithium ion battery comprising same | |
| CN114864870A (en) | Negative pole piece and lithium ion battery comprising same | |
| KR20160051199A (en) | Electrode-adhesive layer composite, method of producing the same, and secondary battery comprising the same | |
| WO2023078409A1 (en) | Separator and lithium ion battery comprising same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |