CN113224461A - High-temperature-resistant lithium ion battery diaphragm and preparation method and application thereof - Google Patents
High-temperature-resistant lithium ion battery diaphragm and preparation method and application thereof Download PDFInfo
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- CN113224461A CN113224461A CN202110338113.2A CN202110338113A CN113224461A CN 113224461 A CN113224461 A CN 113224461A CN 202110338113 A CN202110338113 A CN 202110338113A CN 113224461 A CN113224461 A CN 113224461A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 137
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 137
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 claims abstract description 76
- 239000003063 flame retardant Substances 0.000 claims abstract description 76
- 239000011248 coating agent Substances 0.000 claims abstract description 59
- 238000000576 coating method Methods 0.000 claims abstract description 59
- 239000000758 substrate Substances 0.000 claims abstract description 29
- 239000011159 matrix material Substances 0.000 claims abstract description 22
- 229920000098 polyolefin Polymers 0.000 claims abstract description 17
- 229920000642 polymer Polymers 0.000 claims description 28
- 239000004743 Polypropylene Substances 0.000 claims description 23
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 14
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 13
- DQJJMWZRDSGUJP-UHFFFAOYSA-N ethenoxyethene;furan-2,5-dione Chemical compound C=COC=C.O=C1OC(=O)C=C1 DQJJMWZRDSGUJP-UHFFFAOYSA-N 0.000 claims description 13
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 12
- 238000000354 decomposition reaction Methods 0.000 claims description 11
- ZSIAUFGUXNUGDI-UHFFFAOYSA-N hexan-1-ol Chemical compound CCCCCCO ZSIAUFGUXNUGDI-UHFFFAOYSA-N 0.000 claims description 8
- GETQZCLCWQTVFV-UHFFFAOYSA-N trimethylamine Chemical compound CN(C)C GETQZCLCWQTVFV-UHFFFAOYSA-N 0.000 claims description 8
- -1 polyethylene Polymers 0.000 claims description 7
- 238000002390 rotary evaporation Methods 0.000 claims description 6
- LAMUXTNQCICZQX-UHFFFAOYSA-N 3-chloropropan-1-ol Chemical compound OCCCCl LAMUXTNQCICZQX-UHFFFAOYSA-N 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 3
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 239000003960 organic solvent Substances 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 238000004880 explosion Methods 0.000 abstract description 6
- 230000008018 melting Effects 0.000 abstract description 6
- 238000002844 melting Methods 0.000 abstract description 6
- 229910010272 inorganic material Inorganic materials 0.000 abstract description 4
- 239000011147 inorganic material Substances 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 44
- 239000003792 electrolyte Substances 0.000 description 18
- 239000011247 coating layer Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 13
- 239000000463 material Substances 0.000 description 13
- 238000002485 combustion reaction Methods 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 5
- 230000002349 favourable effect Effects 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 238000002411 thermogravimetry Methods 0.000 description 4
- 230000004580 weight loss Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 150000008064 anhydrides Chemical group 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 125000001453 quaternary ammonium group Chemical group 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 150000008065 acid anhydrides Chemical group 0.000 description 1
- 125000003342 alkenyl group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007142 ring opening reaction Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
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- C08F8/44—Preparation of metal salts or ammonium salts
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2200/00—Safety devices for primary or secondary batteries
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- 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
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Abstract
The invention relates to a high-temperature-resistant lithium ion battery diaphragm and a preparation method and application thereof. qpvmma is a quaternized modified polymethylvinylether-maleic anhydride. Because the melting temperature of the flame retardant coating coated on the surface of the substrate layer is higher than that of the substrate layer, when the lithium ion battery is overheated, the substrate layer is protected by the flame retardant coating and is not easy to melt, so that the thermal runaway, even burning and explosion of the lithium ion battery caused by the damage of the diaphragm are avoided, the flame retardant property of the lithium ion battery diaphragm is greatly improved, and the safety of the high-temperature resistant lithium ion battery diaphragm is higher compared with the traditional polyolefin diaphragm. In addition, the flame-retardant coating has good compatibility with the matrix layer, and has better stability compared with the polyolefin diaphragm coated by the traditional inorganic material, the flame-retardant coating is firmly combined with the matrix layer, and the flame-retardant coating is not easy to peel.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a high-temperature-resistant lithium ion battery diaphragm and a preparation method and application thereof.
Background
Lithium ion batteries are a type of battery that uses a material containing lithium as an electrode and relies on lithium ions to move between a positive electrode and a negative electrode to operate. Lithium ion batteries are a class of lithium batteries that have many advantages such as high energy density, high power density, and long cycle life, and thus have drawn great attention in the fields of portable electronic devices, power batteries, energy storage batteries, and the like. The lithium ion battery mainly comprises a positive electrode material, a negative electrode material, electrolyte, a diaphragm, a related content packaging material and the like. Because the use is improper, the thermal runaway of the lithium ion battery component is easily caused, so that the direct combustion or the participation in the combustion occurs, and the great threat is caused to the safe use of the lithium ion battery. Among them, when accidents such as ignition and explosion occur in the lithium ion battery, the diaphragm and the electrolyte are main inflammable substances.
Specifically, the diaphragm is a specially-formed polymer film, has a microporous structure, and can allow lithium ions in the lithium ion battery to freely pass through, but electrons cannot pass through. The main function of the diaphragm in the lithium ion battery is to isolate the positive electrode and the negative electrode so as to prevent the problems of self discharge of the lithium ion battery, short circuit of the two electrodes and the like. However, when the conventional polyolefin diaphragm is adopted, the lithium ion battery is easily subjected to the condition of overhigh local temperature under the condition of high-power charging and discharging or overcharging, so that the diaphragm inside the battery is heated and shrunk to further cause short circuit of the battery, and the lithium ion battery is exploded and burnt, thereby having great potential safety hazards. Therefore, the flame retardant modification of the high temperature resistant lithium ion battery separator is receiving wide attention.
The membrane material modification mainly comprises two modes of bulk phase doping and surface coating. Wherein, the surface coating modification means that the surface of the diaphragm substrate material is coated with a flame retardant material. Generally, the flame-retardant modified material of the polyolefin separator is a flame-retardant inorganic material, and has poor coating property on the polyolefin separator, so that the coating is easy to peel off after the polyolefin separator is soaked in an electrolyte for a long time, and the flame-retardant property of the polyolefin separator is difficult to guarantee.
Disclosure of Invention
Therefore, a high-temperature-resistant lithium ion battery separator with good stability and good flame retardance and a preparation method and application thereof are needed.
In one aspect of the invention, the invention provides a high-temperature-resistant lithium ion battery diaphragm, which comprises a substrate layer and a flame-retardant coating coated on at least one surface of the substrate layer; the flame retardant coating comprises a polymer having the following general formula (I):
wherein the ratio of m to n is 1: (2-3); the weight average molecular weight of the polymer is 2-10 ten thousand g/mol.
In some of these embodiments, the matrix layer is selected from one of a polyethylene matrix layer, a polypropylene matrix layer, and a polyethylene oxide matrix layer.
In some embodiments, the tensile strength of the high-temperature-resistant lithium ion battery separator is 16N/25 mm-30N/25 mm.
In some embodiments, the initial decomposition temperature of the high-temperature resistant lithium ion battery separator is 313-515 ℃.
In some embodiments, the high-temperature resistant lithium ion battery separator has a specific surface area of13m2/g～64m2/g。
In some of these embodiments, the thickness of the base layer is 30 μm; the thickness of the flame-retardant coating is 3-15 μm, and the flame-retardant coating is a layer formed by the polymer of the general formula (I).
The invention also provides a preparation method of the high-temperature-resistant lithium ion battery diaphragm, which comprises the following steps:
and dissolving the polymer in an organic solvent, uniformly coating the polymer on the surface of a polyolefin substrate, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm.
In some of these examples, the polymer is prepared according to the following steps:
dissolving polymethyl vinyl ether-maleic anhydride in toluene;
adding 3-chloropropanol and N, N-dimethylformamide into a polymethyl vinyl ether-maleic anhydride solution, and reacting for 12-18 h at 100 ℃;
adding hexanol, and continuing to react for 18-24 h at 100 ℃;
performing rotary evaporation and drying to obtain an intermediate;
dissolving the intermediate in isopropanol at room temperature, adding trimethylamine into the intermediate solution, and reacting at 70 ℃ for 12-18 h;
and (4) performing rotary evaporation and drying to obtain the polymer.
In another aspect of the invention, a lithium ion battery is also provided, and the above high temperature resistant lithium ion battery separator is used.
In another aspect of the invention, a rechargeable product is also provided, which contains the lithium ion battery.
The invention has at least the following beneficial effects:
the high-temperature-resistant lithium ion battery diaphragm comprises a substrate layer and a flame-retardant coating which is coated on the surface of the substrate layer and contains a specific polymer. Because the surface of the matrix layer is coated with the flame-retardant coating, the decomposition temperature of the flame-retardant coating is higher, when the interior of the lithium ion battery is overheated, the matrix layer is protected by the flame-retardant coating and is not easy to melt, so that the thermal runaway, even burning and explosion of the lithium ion battery caused by the damage of the diaphragm are avoided, the flame retardant property of the lithium ion battery diaphragm is greatly improved, and the safety of the high-temperature-resistant lithium ion battery diaphragm is higher compared with the traditional polyolefin diaphragm. In addition, the flame-retardant coating of the high-temperature-resistant lithium ion battery diaphragm is a quaternized modified polymer, has good compatibility with the matrix layer, has better stability compared with the polyolefin diaphragm coated by the traditional inorganic material, and is firmly combined with the matrix layer, and the flame-retardant coating is not easy to peel off from the matrix layer after being soaked in electrolyte for a long time. And the quaternized modified polymer has good compatibility with the electrolyte, is favorable for improving the wettability of the diaphragm, and is favorable for the electrolyte and lithium ions to penetrate through the diaphragm.
The preparation method of the high-temperature-resistant lithium ion battery diaphragm is simple to operate, low in cost and capable of realizing large-scale production, and the prepared high-temperature-resistant lithium ion battery diaphragm has good stability and flame retardant property.
The lithium ion battery comprises the high-temperature-resistant lithium ion battery diaphragm, and the diaphragm material has good thermal stability and flame retardant property, so that the diaphragm material is not easy to melt when heated, thereby avoiding thermal runaway and even combustion and explosion caused by short circuit of the anode and the cathode of the battery due to the melting of the diaphragm, and greatly improving the safety of the lithium ion battery. The lithium ion battery is expected to be applied to a plurality of fields such as power batteries, energy storage batteries and the like.
Drawings
Fig. 1 is a schematic structural diagram of a high temperature resistant lithium ion battery separator according to an embodiment of the invention;
FIG. 2 is a thermogravimetric analysis (TGA) profile of quaternized polymethylvinylether-maleic anhydride (qPMVMMA) in a flame retardant coating in an embodiment of the present invention;
FIG. 3 is a graph of the infrared absorption (FT-IR) spectra of PMVMMA (a) and QPMVMMA (b) in accordance with one embodiment of the present invention; wherein, the Wavenumber (cm) of the abscissa-1) Represents wave number (cm)-1) T (%) on the ordinate is light transmittance (%);
FIG. 4 is a Scanning Electron Microscope (SEM) image of the surface of the high temperature resistant lithium ion battery separator of example 3 in accordance with the present invention; wherein the scale bar of a is 100 μm, and the scale bar of b is 1 μm;
FIG. 5 is a temperature rise diagram of lithium ion batteries respectively prepared from a high temperature resistant lithium ion battery separator of example 3 of the present invention and a separator of comparative example 1; wherein the abscissa is time (seconds) and the ordinate is temperature (degrees celsius).
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. In the description of the present invention, it is to be understood that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, an embodiment of the present invention provides a high temperature resistant lithium ion battery separator 10, which includes a substrate layer 110, and a first flame retardant coating 121 and a second flame retardant coating 122 coated on a surface of the substrate layer 110. The first and second flame retardant layers 121 and 122 include a polymer having the following general formula (I):
wherein the ratio of m to n is 1: (2-3); the weight average molecular weight of the polymer is 2-10 ten thousand g/mol.
It is understood that in other specific examples, the high-temperature-resistant lithium ion battery separator may be formed with a flame-retardant coating layer only on one side surface thereof.
The high-temperature-resistant lithium ion battery separator 10 comprises a substrate layer 110, and a first flame-retardant coating layer 121 and a second flame-retardant coating layer 122 which are coated on the surface of the substrate layer 110 and comprise specific polymers. The polymer quaternized polymethylvinylether-maleic anhydride (qPMVMMA) is quaternized modified polymethylvinylether-maleic anhydride. Referring to fig. 2, a thermogravimetric analysis (TGA) graph of the quaternized polymethylvinylether-maleic anhydride (qpvmma) shows that the thermal weight loss of the quaternized polymethylvinylether-maleic anhydride (qpvmma) is mainly divided into three sections, and the first section weight loss temperature is 150 degrees centigrade, which is due to the degradation of quaternary ammonium groups and anhydride groups; the second-stage weight loss temperature is 350 ℃, which is caused by the degradation of a polymer chain; the third segment weight loss temperature is 450 degrees centigrade, which is due to the carbonization of molecules. It can be seen that the thermal decomposition temperature of the quaternized polymethylvinylether-maleic anhydride (qpvmma) is significantly higher than the melting point of conventional polyolefin separators (about 130 degrees celsius).
Therefore, because the surface of the substrate layer 110 is coated with the first flame-retardant coating 121 and the second flame-retardant coating 122, the melting temperature of the first flame-retardant coating 121 and the second flame-retardant coating 122 is higher, when the interior of the lithium ion battery is overheated, the substrate layer 110 is protected by the first flame-retardant coating 121 and the second flame-retardant coating 122, and the melting is not easy to occur, so that the thermal runaway, even combustion and explosion of the lithium ion battery caused by the damage of the diaphragm are avoided, the flame retardant property of the lithium ion battery diaphragm is greatly improved, and compared with the traditional polyolefin diaphragm, the safety of the high-temperature-resistant lithium ion battery diaphragm is higher.
In addition, the first flame-retardant coating 121 and the second flame-retardant coating 122 of the high-temperature-resistant lithium ion battery diaphragm comprise quaternized modified polymers, so that the high-temperature-resistant lithium ion battery diaphragm has good compatibility with the substrate layer 110, has better stability compared with a polyolefin diaphragm coated by a traditional inorganic material, is firmly combined with the substrate layer, and is not easy to peel off from the substrate layer after being soaked in electrolyte for a long time. And the quaternized modified polymer has good compatibility with the electrolyte, is favorable for improving the wettability of the diaphragm, and is favorable for the electrolyte and lithium ions to penetrate through the diaphragm.
In some of these embodiments, the substrate layer 110 is a polyolefin substrate layer. In some of these embodiments, the matrix layer may be one of a polyethylene (PP) matrix layer, a Polypropylene (PE) matrix layer, and a polyethylene oxide matrix layer.
In some embodiments, the tensile strength of the high temperature resistant lithium ion battery separator is 16N/25mm to 30N/25 mm. The tensile strength of the high-temperature-resistant lithium ion battery diaphragm meets the strength requirement of the lithium ion battery diaphragm.
In some embodiments, the high temperature resistant lithium ion battery separator has an initial decomposition temperature of 313 to 515 degrees celsius. The initial decomposition temperature is a temperature at which the mass loss is 20%. The initial decomposition temperature of the high-temperature resistant lithium ion battery diaphragm is obviously higher than that of the traditional polyolefin diaphragm. In some embodiments, the high temperature lithium ion battery separator has an initial decomposition temperature of 343 degrees celsius to 515 degrees celsius. In some embodiments, the high temperature lithium ion battery separator has an initial decomposition temperature of 460 to 515 degrees celsius.
In some embodiments, the specific surface area of the high-temperature-resistant lithium ion battery separator is 13m2/g～64m2(ii) in terms of/g. The specific surface area of the high-temperature-resistant lithium ion battery diaphragm is improved compared with that of the traditional polyolefin diaphragm, so that the porosity of the high-temperature-resistant lithium ion battery diaphragm is improved, and the high-temperature-resistant lithium ion battery diaphragm is beneficial to the passing of electrolyte and lithium ions. In some embodiments, the specific surface area of the high-temperature-resistant lithium ion battery separator is 16m2/g～64m2/g。
In some embodiments, the high-temperature resistant lithium ion battery separator has a unit mass absorption electrolyte mass of 3.3g to 4.8 g. The electrolyte of the high-temperature-resistant lithium ion battery diaphragm has good wettability, and is favorable for the electrolyte to pass through the diaphragm material.
In some of these embodiments, the thickness of the base layer 110 is 30 μm; the first flame-retardant coating layer 121 and the second flame-retardant coating layer 122 are both 3 μm to 15 μm thick, and the first flame-retardant coating layer 121 and the second flame-retardant coating layer 122 are layers formed of the polymer of the general formula (I). As the thickness of the first flame-retardant coating layer 121 and the second flame-retardant coating layer 122 increases, the initial decomposition temperature and the specific surface area of the lithium ion battery separator also increase, but the tensile strength decreases. When the thickness of the first flame-retardant coating 121 and the second flame-retardant coating 122 exceeds 15 μm, the tensile strength of the separator material is difficult to meet the requirement of the lithium ion battery separator.
Preferably, the thickness of the base layer 110 is 30 μm; the thicknesses of the first flame-retardant coating layer 121 and the second flame-retardant coating layer 122 are both 5 to 15 μm. The high-temperature-resistant lithium ion battery diaphragm with the thickness has both thermal stability and electrolyte wettability, the diaphragm is high in mechanical strength and not prone to deformation, and the first flame-retardant coating 121 and the second flame-retardant coating 122 are not prone to peeling from the substrate layer 110. More preferably, the thickness of the base layer 110 is 30 μm; the thickness of each of the first flame-retardant coating layer 121 and the second flame-retardant coating layer 122 is 10 μm. It should be noted that the thicknesses of the base layer 110, the first flame retardant coating layer 121, and the second flame retardant coating layer 122 in the separator are not limited to the above ranges, and the thickness of the separator may be proportionally adjusted according to the size of the lithium ion battery.
The invention also provides a preparation method of the high-temperature-resistant lithium ion battery diaphragm, which comprises the following steps:
and dissolving the polymer in an organic solvent, uniformly coating the polymer on the surface of the substrate, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm.
The preparation method of the high-temperature-resistant lithium ion battery diaphragm is simple to operate, low in cost and capable of realizing large-scale production, and the prepared high-temperature-resistant lithium ion battery diaphragm has good stability and flame retardant property.
In some of these examples, quaternized polymethylvinylether-maleic anhydride (qPMVMMA) was prepared according to steps S11-S16. The specific synthetic route is as follows:
step S11: dissolving polymethyl vinyl ether-maleic anhydride in toluene;
step S12: adding 3-chloropropanol and N, N-Dimethylformamide (DMF) into a polymethyl vinyl ether-maleic anhydride solution, and reacting for 12-18 h at 100 ℃;
step S13: adding hexanol, and continuing to react for 18-24 h at 100 ℃;
step S14: performing rotary evaporation and drying to obtain an intermediate;
step S15: dissolving the intermediate in isopropanol at room temperature, adding trimethylamine into the intermediate solution, and reacting at 70 ℃ for 12-18 h;
step S16: rotary evaporation and drying to obtain the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA).
Specifically, in an embodiment of the present invention, quaternized polymethylvinylether-maleic anhydride (qpvmma) is prepared as follows:
5g of polymethylvinylether-maleic anhydride (PMVMA) was dissolved in a conical flask containing 50mL of toluene, and 1mL of 3-chloropropanol and 1mL of N, N-dimethylformamide were sequentially added to the solution. The mixture was kept at 100 ℃ with continuous stirring for 12 hours. Then, 2mL of hexanol was added to the reaction solution to react with the unreacted acid anhydride unit, and reacted at 100 ℃ for 24 hours. After the reaction, the solvent was removed from the reaction mixture in a rotary vacuum evaporator at 90 ℃ to obtain an intermediate (esterified PMVMA).
The resulting intermediate was dissolved in 100mL of isopropanol at room temperature. To the intermediate solution was added 20mL of trimethylamine, stirred at 70 ℃ for 12 hours, and then the solvent was removed at 70 ℃ in a rotary vacuum evaporator to give quaternized polymethylvinylether-maleic anhydride (qPMVMMA).
Referring to FIG. 3, there are shown quaternized polymethylvinylether-maleic anhydride (qPMVMMA) (a) and quaternized polymethylethylene prepared in accordance with the present embodimentInfrared absorption spectrum of alkenyl ether-maleic anhydride (qPMVMMA) (b). It can be seen that PMVMA is at 2800cm-1And 2950cm-1With several typical vibration bands in between, from-CH3、-CH2；1730cm-1-CO being an anhydride group. In the spectrum of the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA), 955cm-1Is- (CH)3)2N+-a group. These characteristic absorption peaks indicate that the ring-opening reaction was successfully performed during the synthesis and that quaternary ammonium groups were successfully introduced on the backbone polymer.
The invention also provides a lithium ion battery, which uses the high-temperature-resistant lithium ion battery diaphragm.
The lithium ion battery comprises the high-temperature-resistant lithium ion battery diaphragm, and the diaphragm material has good thermal stability and flame retardant property, so that the diaphragm material is not easy to melt when heated, thereby avoiding thermal runaway and even combustion and explosion caused by short circuit of the anode and the cathode of the battery due to the melting of the diaphragm, and greatly improving the safety of the lithium ion battery. The lithium ion battery is expected to be applied to a plurality of fields such as power batteries, energy storage batteries and the like.
The invention also provides a rechargeable product which contains the lithium ion battery.
The high temperature resistant lithium ion battery separator of the present invention is further illustrated by the following specific examples.
Example 1:
and (2) dissolving the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA) in an isopropanol solution, uniformly coating the dissolved solution on a PP substrate after complete dissolution, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm of the embodiment 1. Wherein the thickness of the flame-retardant coating is 3 μm, and the thickness of the PP basal layer is 30 μm.
Example 2:
and (3) dissolving the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA) in an isopropanol solution, uniformly coating the dissolved solution on a PP substrate after complete dissolution, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm of the embodiment 2. Wherein the thickness of the flame-retardant coating is 5 μm, and the thickness of the PP basal layer is 30 μm.
Example 3:
and (3) dissolving the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA) in an isopropanol solution, uniformly coating the dissolved solution on a PP substrate after complete dissolution, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm of the embodiment 3. Wherein the thickness of the flame-retardant coating is 10 μm, and the thickness of the PP basal layer is 30 μm.
Referring to fig. 4, a Scanning Electron Microscope (SEM) of the surface of the high temperature resistant lithium ion battery separator of example 3 shows that the surface of the high temperature resistant lithium ion battery separator coated with the quaternized polymethylvinylether-maleic anhydride (qpvmma) flame retardant coating has a porous structure with a high porosity, which is beneficial to the back and forth shuttling of ions during the charging and discharging processes of the lithium ion battery, and does not affect the electrochemical performance of the lithium ion battery.
Example 4:
and (3) dissolving the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA) in an isopropanol solution, uniformly coating the dissolved solution on a PP substrate after complete dissolution, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm of the embodiment 4. Wherein the thickness of the flame-retardant coating is 15 μm, and the thickness of the PP basal layer is 30 μm.
Comparative example 1:
the lithium ion battery separator of comparative example 1 was a PP separator having a thickness of 30 μm.
Comparative example 2:
and (3) dissolving the quaternized polymethyl vinyl ether-maleic anhydride (qPMVMMA) in isopropanol solution, uniformly coating the dissolved solution on a PP matrix after complete dissolution, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm of the comparative example 2. Wherein the thickness of the flame-retardant coating is 30 μm, and the thickness of the PP basal layer is 30 μm.
TABLE 1
As can be seen from the data in Table 1, the initial decomposition temperature of the high-temperature resistant lithium ion battery separator of examples 1 to 4 is significantly increased at 313 ℃ to 515 ℃ compared with the conventional PP separator of comparative example 1The thermal stability is better than that of the comparative example 1, and the diaphragm is not easy to damage at high temperature, so that the high-temperature-resistant lithium ion battery diaphragms of the embodiments 1-4 have good flame retardant property. Meanwhile, the applicant researches and discovers that the flame-retardant coating of the diaphragm in the embodiment 1-4 has a high-porosity structure, and the specific surface area (13 m) of the diaphragm material can be increased2/g～64m2/g) to facilitate the passage of electrolyte and lithium ions. Compared with the PP diaphragm of the comparative example 1, the diaphragms of the embodiments 1 to 4 have the advantages that the tensile strength (16N/25 mm-30N/25 mm) is reduced, but the strength requirement of the lithium ion battery diaphragm can be met, the flame-retardant coating is firmly combined with the PP matrix layer, the coating is not easy to peel off after long-term use, and the safety of the lithium ion battery diaphragm is ensured.
Compared with the traditional PP diaphragm of the comparative example 1, the high-temperature-resistant lithium ion battery diaphragms of the embodiments 1 to 4 have the advantage that the mass of the electrolyte absorbed by the unit mass is increased, which also shows that the improvement of the porosity and the wettability of the lithium ion battery diaphragm by the flame-retardant coating is beneficial to the electrolyte to pass through the lithium ion battery diaphragm.
The thickness of the flame-retardant coating of the lithium ion battery diaphragm in the comparative example 2 is 30 micrometers, the thickness of the PP base layer is 30 micrometers, and compared with the lithium ion battery diaphragms in the examples 1-4, the thickness of the flame-retardant coating is obviously increased. The initial decomposition temperature, the specific surface area and the unit mass absorption electrolyte mass of the comparative example 2 are all higher than those of the lithium ion battery separators of the examples 1-4, but the tensile strength is 12N/25mm, so that the strength requirement of the separator material is difficult to meet.
The flame retardant effect was examined by simulating the change in the temperature of the lithium ion battery in the thermal runaway process of the lithium ion battery, and reference is made to fig. 5, which is a temperature rise diagram of the lithium ion battery separator of example 3 and comparative example 1. It can be seen that the rate of temperature rise of the lithium ion battery using the separator of example 3 is relatively small. The lithium ion battery using the PP separator of comparative example 1 had a large temperature rise rate, and the lithium ion battery generated thermal runaway. When the temperature of the lithium ion battery is heated to 300 seconds, the temperature of the PP diaphragm lithium ion battery rises to 276 ℃, but the temperature of the lithium ion battery of the diaphragm in the embodiment 3 is only 200 ℃, which shows that the heat transfer of the lithium ion battery can be effectively reduced by adding the qPMVMMA flame-retardant coating.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The high-temperature-resistant lithium ion battery diaphragm is characterized by comprising a substrate layer and a flame-retardant coating coated on at least one surface of the substrate layer; the flame retardant coating comprises a polymer having the following general formula (I):
wherein the ratio of m to n is 1: (2-3); the weight average molecular weight of the polymer is 2-10 ten thousand g/mol.
2. The lithium ion battery separator according to claim 1, wherein the matrix layer is selected from one of a polyethylene matrix layer, a polypropylene matrix layer, and a polyethylene oxide matrix layer.
3. The high temperature resistant lithium ion battery separator according to claim 1, wherein the tensile strength of the high temperature resistant lithium ion battery separator is 16N/25mm to 30N/25 mm.
4. The high temperature resistant lithium ion battery separator according to claim 1, wherein the initial decomposition temperature of the high temperature resistant lithium ion battery separator is 313-515 degrees Celsius.
5. The high temperature resistant lithium ion battery separator according to claim 1, wherein the high temperature resistant lithium ion battery separator has a specific surface area of 13m2/g～64m2/g。
6. The high temperature resistant lithium ion battery separator of any of claims 1-5, wherein the matrix layer has a thickness of 30 μm; the thickness of the flame-retardant coating is 3-15 μm, and the flame-retardant coating is a layer formed by the polymer of the general formula (I).
7. The preparation method of the high-temperature-resistant lithium ion battery separator according to any one of claims 1 to 6, characterized by comprising the following steps:
and dissolving the polymer in an organic solvent, uniformly coating the polymer on the surface of a polyolefin substrate, and drying to obtain the high-temperature-resistant lithium ion battery diaphragm.
8. The preparation method of the high-temperature-resistant lithium ion battery separator according to claim 7, wherein the polymer is prepared according to the following steps:
dissolving polymethyl vinyl ether-maleic anhydride in toluene;
adding 3-chloropropanol and N, N-dimethylformamide into a polymethyl vinyl ether-maleic anhydride solution, and reacting for 12-18 h at 100 ℃;
adding hexanol, and continuing to react for 18-24 h at 100 ℃;
performing rotary evaporation and drying to obtain an intermediate;
dissolving the intermediate in isopropanol at room temperature, adding trimethylamine into the intermediate solution, and reacting at 70 ℃ for 12-18 h;
and (4) performing rotary evaporation and drying to obtain the polymer.
9. A lithium ion battery using the high temperature resistant lithium ion battery separator according to any one of claims 1 to 7.
10. A rechargeable product comprising the lithium ion battery according to claim 9.
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| JP2013251205A (en) * | 2012-06-01 | 2013-12-12 | Mitsubishi Paper Mills Ltd | Coating liquid for lithium ion battery separator and lithium ion battery separator |
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| CN109449351A (en) * | 2018-11-20 | 2019-03-08 | 孙培丽 | A kind of lithium battery diaphragm and preparation method thereof |
| CN111244362A (en) * | 2020-01-15 | 2020-06-05 | 惠州锂威新能源科技有限公司 | Composite diaphragm, preparation method thereof and lithium ion battery |
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| JP2010049874A (en) * | 2008-08-20 | 2010-03-04 | Toyo Ink Mfg Co Ltd | Composition for battery |
| JP2013251205A (en) * | 2012-06-01 | 2013-12-12 | Mitsubishi Paper Mills Ltd | Coating liquid for lithium ion battery separator and lithium ion battery separator |
| CN104937742A (en) * | 2012-12-28 | 2015-09-23 | Sk新技术株式会社 | Micro-porous hybrid film having electro-chemical stability and method for preparing the same |
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