CN113054324A - High-safety diaphragm and battery - Google Patents
High-safety diaphragm and battery Download PDFInfo
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- CN113054324A CN113054324A CN202110429906.5A CN202110429906A CN113054324A CN 113054324 A CN113054324 A CN 113054324A CN 202110429906 A CN202110429906 A CN 202110429906A CN 113054324 A CN113054324 A CN 113054324A
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Images
Classifications
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the field of battery separators, in particular to a high-safety separator and a battery, which comprise a porous base material, a heat-resistant coating coated on at least one side of the porous base material, and a low-closed pore temperature coating coated on the porous base material or the heat-resistant coating; the heat-resistant coating comprises a heat-resistant resin; the low closed cell temperature coating comprises a self-closing cell material; the self-closing pore material comprises an adhesive self-closing resin with a low melting temperature or a low viscous flow temperature. The film breaking temperature and the heat-resistant shrinkage performance of the diaphragm are improved by arranging the heat-resistant coating, meanwhile, the low-closed-hole-temperature coating is introduced, the cohesive self-closing resin with low melting temperature or low viscous flow temperature can be quickly melted or softened at a certain temperature, the pores of the porous base film are closed, the purpose of reducing the closed hole temperature is achieved, the difference value of the closed hole temperature and the film breaking temperature is improved, the high-safety diaphragm is obtained, and the safety of the battery is enhanced.
Description
Technical Field
The invention relates to the field of battery diaphragms, in particular to a high-safety diaphragm and a battery.
Background
The lithium ion battery generally mainly comprises a positive electrode, a negative electrode, a diaphragm, an electrolyte and a battery shell. In the structure of the lithium ion battery, a diaphragm is one of key inner layer components. The closed pore temperature and the rupture temperature of the diaphragm are main parameters for measuring the safety performance of the diaphragm. When the internal temperature of the battery cell reaches the closed pore temperature of the diaphragm, the diaphragm micropores generate a self-closing phenomenon, the continuous transmission of lithium ions is blocked, and an open circuit is formed, so that the battery cell is protected. When the temperature inside the battery cell is higher than the closed pore temperature to reach the membrane breaking temperature of the membrane, the fused mass of the membrane is broken, the short circuit inside the battery cell is caused, and the explosion risk exists. Therefore, to improve the safety of lithium ion batteries, the ideal separator requires a low closed cell temperature and a high rupture temperature.
The adhesive functional coating film is a common lithium ion battery diaphragm type, a porous substrate is coated with a coating with an adhesive function, and a pole piece of a battery can be adhered to the diaphragm through a hot pressing process. The common adhesive functional coating material is fluorine-containing resin or acrylic resin, and the adhesive functional coating prepared from the fluorine-containing resin and the acrylic resin does not have a self-closing function or has a high closing temperature.
Disclosure of Invention
The invention provides a diaphragm with excellent heat resistance and safety performance,
the purpose of the invention is realized by the following technical scheme:
the invention provides a high-safety diaphragm, which comprises a porous base material, a heat-resistant coating coated on at least one side of the porous base material, and a low-closed pore temperature coating coated on the porous base material or the heat-resistant coating;
the heat-resistant coating comprises a heat-resistant resin;
the low closed cell temperature coating comprises a self-closing cell material; the self-closing pore material comprises an adhesive self-closing resin having a low melting temperature or a low viscous flow temperature.
The invention also provides a battery comprising the high-safety diaphragm.
Compared with the prior art, the invention has the following positive effects:
the film breaking temperature and the heat-resistant shrinkage performance of the diaphragm are improved by arranging the heat-resistant coating, meanwhile, the low-closed-hole-temperature coating is introduced, the cohesive self-closing resin with low melting temperature or low viscous flow temperature can be quickly melted or softened at a certain temperature, the pores of the porous base film are closed, the purpose of reducing the closed hole temperature is achieved, the difference value of the closed hole temperature and the film breaking temperature is improved, the high-safety diaphragm is obtained, and the safety of the battery is enhanced.
Drawings
Fig. 1 is a schematic structural view of a high safety separator and a battery according to the present invention.
Wherein: 1-adhesive self-closing resin; 2-inorganic particles; 3-a porous substrate; 4-heat resistant resin; 5-Binder resin
Detailed Description
Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description set forth herein is intended as a preferred example for purposes of illustration only and is not intended to limit the scope of the present disclosure, so it is to be understood that other equivalents and modifications may be made without departing from the spirit and scope of the present disclosure.
In order to improve the safety of the battery during use, the invention provides a high-safety diaphragm with low closed pore temperature, high film breaking temperature and excellent high-temperature resistance.
The method specifically comprises the following steps: a high-safety separator includes a porous substrate, and a heat-resistant coating layer coated on at least one side of the porous substrate, and a low closed-cell temperature coating layer coated on the porous substrate or the heat-resistant coating layer; the heat-resistant coating comprises a heat-resistant resin; the low closed cell temperature coating comprises a self-closing cell material; the self-closing pore material comprises an adhesive self-closing resin having a low melting temperature or a low viscous flow temperature. The heat-resistant coating serves as a framework result of the high-safety diaphragm, high mechanical strength can be kept before the melting temperature or the decomposition temperature is reached, the film breaking temperature of a coating film can be effectively increased, the low-closed-pore-temperature coating containing the adhesive self-closing resin with low melting temperature or low viscous flow temperature can be rapidly melted or softened when the temperature inside the battery is abnormal, the continuous transmission of lithium ions is blocked, an open circuit is formed, and the battery core is further protected.
Considering that the procedures of high-temperature hot-pressing baking and the like are often required in the manufacturing process of the battery core, the closed pore temperature of the diaphragm cannot be too low, the phenomenon that irreversible closed pores occur in the hot processing process to influence the use of the battery core is avoided, the melting temperature (Tm) or viscous flow temperature (Tf) of the adhesive self-closing resin can be limited, and the smaller value of the Tm and the Tf satisfies that Tm/Tf is more than or equal to 100 ℃ and less than or equal to 120 ℃.
In the hot-pressing process of the battery core, the temperature of the hot-pressing bonding condition of the battery core is often lower than 90 ℃, when the crystallinity of the adhesive self-closing resin is too high, the material can show the characteristics of a crystalline material, and the material can soften to show excellent bonding capability only when the temperature is close to the melting temperature.
The present invention is also directed to further increase the rupture temperature of a high-safety separator while achieving a low closed-cell temperature of the high-safety separator, and thus, may be limited to the selection of a heat-resistant resin having a melting temperature of 250 ℃ or more and 250 ℃ or more. Mention may be made of one or more mixtures of polyamides, polyimides, polysulfones, polyether sulfones, polyether imides, polyphenylene sulfides, polyether ether ketones, polyarylates, polyamide imides, polyphenylene oxides.
The size of the pore size in the heat-resistant coating has a great influence on the ion-passing ability of the separator and the heat resistance. When the pore size is too large, the heat-resistant coating does not exert a good suppression effect on the thermal shrinkage of the porous substrate, and the closed-cell temperature may not be able to meet the design requirements due to the discontinuity of the coating. When the pore diameter is too small, the lithium ion-passing ability is reduced and the internal resistance is increased. In the invention, the solid content of the coating slurry in the heat-resistant coating is adjusted to change the conditions of thermally-induced phase separation or phase separation of non-solvent, such as: the temperature, humidity, coagulation bath concentration and other conditions, and the obtained heat-resistant coating has uniform pore size distribution, and Dx represents the pore size when the pore volume accumulation reaches x percent of the total pore volume in the pore size distribution of the coating. The aperture of the heat-resistant coating is not less than 0.01um and not more than D50 and not more than 1.0um, preferably not less than 0.05um and not more than D50 and not more than 0.8um, and D75/D25 is not more than 2. The uniform aperture can ensure that the heat-resistant coating has good continuity, has certain mechanical strength at high temperature, can effectively improve the film breaking temperature and improve the heat-resistant shrinkage performance.
The heat-resistant coating and/or the low-closed-pore-temperature coating also comprise inorganic particles, wherein the inorganic particles such as aluminum oxide, barium sulfate and the like have higher thermal stability, do not generate volume change in the temperature rising process, can increase the heat shrinkage resistance of each coating, are favorable for pore formation of the coating, and more, the inorganic particles are BaTiO3、SrTiO3、BaSO4、SnO2、CeO2、MgO、NiO、CaO、ZnO、ZrO2、SiO2、Y2O3、Al2O3、SiC、TiO2、Mg(OH)2、Al(OH)3、Li7La3Zr2O12、La0.51Li0.34TiO2.94、Li1.3Al0.3Ti1.7(PO4)3、Li2+2xZn1-xGe4One or more mixtures thereof.
In the low-closed pore temperature coating, in order to realize more excellent hot-press bonding performance, not destroy the characteristic of self-closed pores, increase the bonding force among materials of the low-closed pore temperature coating and make requirements on the formula proportion of the low-closed pore temperature coating, adhesive resin and binder resin can be added in the low-closed pore temperature coating, the adhesive resin can be used for increasing the bonding force among the materials of the low-closed pore temperature coating, the binder resin can be used for adjusting the hot-press bonding force of the low-closed pore temperature coating, the weight proportion of the self-closed pore material to the binder resin is specifically limited to 50-99%, the weight proportion of inorganic particles is 0-40%, and the weight proportion of the binder resin is 1-20%; wherein the self-closed pore material accounts for 70-100% of the sum of the weight of the self-closed pore material and the weight of the binder resin.
The binder resin is not particularly limited, and may be at least one of polyacrylic acid, acrylic resin, polyvinyl alcohol, and polyacrylonitrile, which are known in the industry.
The binder resin is not particularly limited, and may be at least one of polyacrylic acid, acrylic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyvinyl alcohol, and the like, which are well known in the industry.
The self-sealing material may be polyvinylidene fluoride copolymer, polyacrylic acid, modified acrylic resin, modified polyacrylonitrile, modified polyolefin, low molecular weight polyolefin, or polyethylene glycol.
As shown in Table 1, the closed pore temperature of the high-safety coating diaphragm prepared by the invention is less than or equal to 120 ℃, and the diaphragm breaking temperature is more than or equal to 200 ℃; the thermal shrinkage in TD and MD directions after being placed for one hour at 150 ℃ is less than or equal to 10 percent, the difference between the closed pore temperature and the film breaking temperature of the high-safety diaphragm is improved as much as possible, and when the battery cell is heated, the heat-resistant coating can inhibit the diaphragm from shrinking, so that short circuit is avoided. In the wider temperature interval from the closed pore temperature to the film breaking temperature, the diaphragm can be closed automatically, the continuous temperature rise of the battery cell is avoided, the diaphragm cannot be damaged due to the loss of mechanical strength, the contact between the positive electrode and the negative electrode is avoided, the serious thermal runaway is avoided, and the safety performance is greatly improved.
The preparation method of the high-safety diaphragm comprises the following steps:
s1, respectively dissolving and dispersing the heat-resistant resin and the inorganic particles in an organic solvent, and mixing to prepare heat-resistant coating slurry;
s2, coating the heat-resistant coating slurry on at least one surface of the porous substrate, removing the solvent by a thermal or non-solvent induced film forming method, and drying to obtain a heat-resistant coating film;
s3, dispersing the adhesive resin with low melting point/viscous flow temperature, the inorganic particles and the binder resin in water to form aqueous coating slurry;
and S4, coating the aqueous coating slurry on at least one surface of the heat-resistant coating film, and drying to obtain the high-safety coating diaphragm shown in figure 1.
The coating method is not limited, and various conventional methods such as wire bar, gravure roll, spin coating, etc. can be used.
A battery comprising any one of the above high safety separators.
The following will further explain the self-partition functional battery separator, the lithium ion battery and the preparation method thereof according to the present invention by combining specific examples and comparative examples.
Example 1
Weighing 0.4Kg of modified para-aramid and dissolving the modified para-aramid into 6Kg of DMAC (dimethylacetamide) containing 4% of calcium chloride cosolvent, grinding and dispersing 0.6Kg of alumina into 4Kg of DMAC, and mixing the aramid solution and the alumina dispersion liquid to prepare aramid coating slurry; the aramid fiber slurry is coated on one side of a 10-micron polyethylene base film in an extrusion coating mode, and is washed and dried after passing through a humidifying drying oven to obtain the aramid fiber coating film with the thickness of 13 microns and the aramid fiber coating thickness of 3 microns.
0.7kg of modified polyethylene wax, 0.2kg of PMMA with large particle size and 0.2kg of polyacrylic acid emulsion adhesive are weighed and uniformly stirred in 10kg of water to prepare adhesive layer coating slurry, the adhesive layer coating slurry is coated on two sides of an aramid fiber coating film in a roller coating mode, and after drying, the thickness of a diaphragm is 16 microns, and the thickness of a double-sided adhesive coating is 3 microns.
Example 2
Weighing 0.7Kg of meta-aramid fiber, dissolving the meta-aramid fiber in 6Kg of NMP, grinding and dispersing 0.3Kg of alumina in 4Kg of NMP, and mixing the aramid fiber solution and the alumina dispersion liquid to prepare aramid fiber coating slurry; aramid slurry is coated on two sides of a 10-micron polyethylene base film in a micro-gravure coating mode, and after washing and drying, the thickness of the obtained aramid coating film is 14 microns, and the thickness of the aramid coating film is 4 microns.
0.6kg of modified polybutylene, 0.15kg of PVDF powder and 0.15kg of polyacrylate emulsion adhesive are weighed and uniformly stirred in 10kg of water to prepare adhesive layer coating slurry, the adhesive layer coating slurry is coated on one side of an aramid fiber coating film in a roller coating mode, and the thickness of a diaphragm is obtained after drying, wherein the thickness of the double-sided adhesive coating is 2 microns.
Example 3
The same procedure as in example 1 was repeated except that the pore size distribution of the heat-resistant layer was adjusted to D75/D25 > 2.
Example 4
The procedure was as in example 2 except that the crystallinity of the adhesive self-closing resin was adjusted to a low melting temperature or a low viscous flow temperature of > 30%.
Example 5
The crystallinity of the adhesive self-closing resin with low melting temperature/low viscous flow temperature is more than 30 percent by the same steps as the rest steps of the example 2 except that the pore size distribution of the heat-resistant layer is adjusted to D75/D25 more than 2.
Comparative example 1
The preparation method comprises the steps of coating CCS slurry on one side of a 10-micron polyethylene base film in an extrusion coating mode, carrying out humidification and drying in a drying oven, then carrying out water washing and drying to obtain a coating film with the thickness of 13 microns and the CCS coating with the thickness of 3 microns, preparing PVDF-HFP bonding layer slurry, measuring the crystallinity of the PVDF-HFP bonding layer slurry to be 18%, coating the PVDF-HFP bonding layer slurry on two sides of the coating film in a roller coating mode, and drying to obtain the PVDF-HFP bonding layer slurry with the thickness of 16 microns and the bonding layer thickness of 3 microns.
Comparative example 2
The preparation method comprises the steps of coating CCS slurry on one side of a 10-micron polyethylene base film in an extrusion coating mode, washing and drying after passing through a humidifying oven to obtain a coating film with the thickness of 13 microns and the thickness of the CCS coating of 3 microns, preparing polyethylene wax bonding layer slurry, measuring the crystallinity of the polyethylene wax bonding layer slurry to be 70%, coating the polyethylene wax bonding layer slurry on two sides of the coating film in a roller coating mode, and drying to obtain the polyethylene base film with the thickness of 16 microns and the thickness of 3 microns.
TABLE 1 comparison of physical Properties, characterizations, and Properties of the examples and comparative examples
(-) indicates the same as example 1, and (\) indicates no implementation or absence of corresponding data.
In examples 1 to 5, after the heat-resistant layer and the adhesive layer are coated, compared with a base material, the film breaking temperature is significantly increased, the hole closing temperature is reduced, the difference between the hole closing temperature and the film breaking temperature is more than 100 ℃, the heat-resistant shrinkage performance of the coating is also excellent, and the safety performance of the battery core is greatly improved. Meanwhile, the bonding coating also has certain bonding capacity, and can meet the requirements of the battery cell processing technology in the fields of square shells, soft packages and the like.
To sum up, this application has designed the diaphragm of the very excellent bonding function of security performance, can have great improvement lithium ion battery's security performance, has huge application prospect.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the concept of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (15)
1. A high-safety separator is characterized by comprising a porous substrate, a heat-resistant coating coated on at least one side of the porous substrate, and a low-closed pore temperature coating coated on the porous substrate or the heat-resistant coating;
the heat-resistant coating comprises a heat-resistant resin;
the low closed cell temperature coating comprises a self-closing cell material; the self-closing pore material comprises an adhesive self-closing resin with a low melting temperature or a low viscous flow temperature.
2. The high safety separator according to claim 1, wherein the adhesive self-closing resin has a melting temperature (Tm) or a viscous flow temperature (Tf), and the smaller of the values of Tm and Tf satisfies 100 ℃ Tm/Tf or more and 120 ℃ or less.
3. The high safety separator according to claim 1, wherein the low melting temperature or low viscous flow temperature adhesive self-closing resin has a crystallinity of less than 30%.
4. The high safety separator according to claim 1, wherein the heat-resistant coating and/or the low closed cell temperature coating further comprise inorganic particles.
5. The high safety separator according to claim 4, wherein said low closed cell temperature coating further comprises a binder resin; the self-closed pore material accounts for 50-99 wt%, the inorganic particles accounts for 0-40 wt%, and the adhesive resin accounts for 1-20 wt%.
6. The high safety separator according to claim 4, wherein said low closed cell temperature coating further comprises a binder resin, a binder resin; the weight ratio of the self-closed pore material to the binder resin is 50-99%, the weight ratio of the inorganic particles is 0-40%, and the weight ratio of the binder resin is 1-20%; wherein the self-closed pore material accounts for 70-100% of the sum of the weight of the self-closed pore material and the weight of the binder resin.
7. The high safety separator according to claim 1, wherein Dx represents a pore size at which pore volumes cumulatively reach x% of the total pore volume in a pore size distribution of the coating, and the heat-resistant coating has a pore size of 0.01 um. ltoreq. D50. ltoreq.1 um, and D75/D25. ltoreq.2.
8. The high-safety separator according to claim 1, wherein the heat-resistant resin has a melting temperature of 250 ℃ or more and 250 ℃ or more.
9. The high safety separator according to claim 1, wherein said self-closing cell material comprises a mixture of one or more of polyvinylidene fluoride copolymers, polyacrylic acid, modified acrylic resins, modified polyacrylonitrile, modified polyolefins, low molecular weight polyolefins, polyethylene glycol.
10. The high-safety separator according to claim 5, wherein the binder resin is at least one of polyacrylic acid, acrylic resin, polyvinyl alcohol, and polyacrylonitrile.
11. The high safety separator according to claim 1, wherein the heat-resistant resin is one or a mixture of more of polyamide, polyimide, polysulfone, polyethersulfone, polyetherimide, polyphenylene sulfide, polyetheretherketone, polyarylate, polyamideimide, and polyphenylene oxide.
12. The high-safety separator according to claim 4, wherein the inorganic particles are BaTiO3、SrTiO3、BaSO4、SnO2、CeO2、MgO、NiO、CaO、ZnO、ZrO2、SiO2、Y2O3、Al2O3、SiC、TiO2、Mg(OH)2、Al(OH)3、Li7La3Zr2O12、La0.51Li0.34TiO2.94、Li1.3Al0.3Ti1.7(PO4)3、Li2+2xZn1-xGe4One or more mixtures thereof.
13. The high-safety separator according to claim 1, wherein the high-safety coated separator has a closed-cell temperature of 120 ℃ or less and a film breaking temperature of 200 ℃ or more.
14. The high safety separator according to claim 1, wherein the high safety separator exhibits a TD and MD heat shrinkage of 10% or less after one hour of storage at 150 ℃.
15. A battery comprising the high-safety separator according to any one of claims 1 to 14.
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Effective date of registration: 20220506 Address after: No. 889, Jieneng Road, equipment manufacturing zone, Gaolan Port Economic Zone, Zhuhai, Guangdong 519000 Applicant after: SHANGHAI ENERGY NEW MATERIALS TECHNOLOGY CO.,LTD. Address before: 201306 No. 155 Nanlu Highway, Pudong New Area, Shanghai Applicant before: SHANGHAI ENJIE NEW MATERIAL TECHNOLOGY Co.,Ltd. |
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Application publication date: 20210629 |