CN116666907A - Lithium battery diaphragm, preparation method thereof, lithium battery comprising lithium battery diaphragm and application of lithium battery diaphragm - Google Patents
Lithium battery diaphragm, preparation method thereof, lithium battery comprising lithium battery diaphragm and application of lithium battery diaphragm Download PDFInfo
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- CN116666907A CN116666907A CN202310170567.2A CN202310170567A CN116666907A CN 116666907 A CN116666907 A CN 116666907A CN 202310170567 A CN202310170567 A CN 202310170567A CN 116666907 A CN116666907 A CN 116666907A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 145
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 133
- 238000002360 preparation method Methods 0.000 title description 13
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 47
- 239000011737 fluorine Substances 0.000 claims abstract description 47
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 47
- 238000000576 coating method Methods 0.000 claims abstract description 28
- 239000011248 coating agent Substances 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 17
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims abstract description 16
- -1 polypropylene Polymers 0.000 claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 12
- 239000004743 Polypropylene Substances 0.000 claims abstract description 7
- 229920001155 polypropylene Polymers 0.000 claims abstract description 7
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical group [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 10
- 239000007774 positive electrode material Substances 0.000 claims description 9
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000011247 coating layer Substances 0.000 claims description 5
- 239000004698 Polyethylene Substances 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- 238000001523 electrospinning Methods 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 229920000306 polymethylpentene Polymers 0.000 claims description 2
- 239000011116 polymethylpentene Substances 0.000 claims description 2
- 239000003792 electrolyte Substances 0.000 abstract description 16
- 238000007086 side reaction Methods 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 16
- 238000012360 testing method Methods 0.000 description 8
- 239000011572 manganese Substances 0.000 description 6
- CQDGTJPVBWZJAZ-UHFFFAOYSA-N monoethyl carbonate Chemical compound CCOC(O)=O CQDGTJPVBWZJAZ-UHFFFAOYSA-N 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000007784 solid electrolyte Substances 0.000 description 5
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 238000011065 in-situ storage Methods 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 description 3
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 3
- 229910013872 LiPF Inorganic materials 0.000 description 3
- 101150058243 Lipf gene Proteins 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000002441 reversible effect Effects 0.000 description 3
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical group O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical group C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000007142 ring opening reaction Methods 0.000 description 2
- LLTOPKQGFAAMKH-UHFFFAOYSA-N siderin Chemical compound COC1=CC(=O)OC2=CC(OC)=CC(C)=C21 LLTOPKQGFAAMKH-UHFFFAOYSA-N 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013716 LiNi Inorganic materials 0.000 description 1
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 1
- 238000001994 activation Methods 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000011162 core material Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- FRMOHNDAXZZWQI-UHFFFAOYSA-N lithium manganese(2+) nickel(2+) oxygen(2-) Chemical compound [O-2].[Mn+2].[Ni+2].[Li+] FRMOHNDAXZZWQI-UHFFFAOYSA-N 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
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
- H01M50/409—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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Cell Separators (AREA)
Abstract
The application provides a lithium battery separator, wherein the separator comprises: the fluorine-containing coating is formed on two sides of the substrate. The application also provides a method for preparing the lithium battery diaphragm, a lithium battery comprising the lithium battery diaphragm and application of the lithium battery diaphragm in the lithium battery. According to the application, a novel lithium battery diaphragm with a sandwich structure is prepared by forming fluorine-containing coatings comprising fluorine-containing materials such as PVDF-HFP copolymers on two sides of a traditional diaphragm such as a polypropylene diaphragm, and the lithium battery diaphragm can reduce the occurrence of interface side reactions and improve the stability of an electrolyte/electrode interface layer, thereby improving the electrochemical performance such as cycle performance and the like of a lithium battery.
Description
Technical Field
The application relates to the field of electrochemistry, in particular to a lithium battery diaphragm, a preparation method thereof, a lithium battery comprising the lithium battery diaphragm and application of the lithium battery diaphragm in a lithium battery.
Background
Lithium metal batteries are a promising technology with metallic lithium as the negative electrode, which can meet the emerging demand for high energy density storage systems due to its high charge density. However, the cycle process of the battery is often accompanied by low Coulombic Efficiency (CE) due to continuous decomposition of the electrolyte, etc., which results in a reduction in the life of the battery, and thus, it is important for the application of the lithium metal battery to improve the cycle performance of the battery.
The separator material is one of important inner layer components of the lithium battery, and is important to the performance of the lithium battery. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. At present, materials such as polyethylene and polypropylene are basically adopted for the commercially used lithium battery separator, but the separators made of the materials have the defects of low porosity, low melting point, poor mechanical properties and the like, and have a certain negative effect on the improvement of the performance of the lithium battery.
Therefore, there is an urgent need for a lithium battery separator that contributes to improving the electrical properties, particularly the cycle properties, of lithium batteries, particularly lithium metal batteries.
Disclosure of Invention
In view of the above, the present application provides a lithium battery separator to further improve electrochemical performance of a lithium battery.
According to a first aspect of the present application, there is provided a lithium battery separator, wherein the separator comprises: the fluorine-containing coating is formed on two sides of the substrate.
According to a second aspect of the present application, there is provided a method of preparing the lithium battery separator according to the first aspect of the present application, wherein the method comprises: preparing a solution containing polyvinylidene fluoride-hexafluoropropylene copolymer as a fluorine-containing material, forming the solution into a fluorine-containing coating layer on both sides of a substrate by wet coating or electrospinning, thereby obtaining the lithium battery separator.
According to a third aspect of the present application there is provided a lithium battery comprising a lithium battery separator according to the first aspect of the present application or a lithium battery separator prepared by a method according to the second aspect of the present application.
According to a fourth aspect of the present application there is provided the use of a lithium battery separator according to the first aspect of the present application or a lithium battery separator prepared by a method according to the second aspect of the present application in a lithium battery.
The present application prepares a new lithium battery separator in a "sandwich" structure by forming fluorine-containing coatings comprising fluorine-containing materials such as PVDF-HFP copolymer on both sides of a conventional separator such as a polypropylene separator, which has certain advantages over existing commercial separators, single-sided fluorine-containing separators, and integrally formed fluorine-containing separators. Firstly, the fluorine-containing coating can reduce the occurrence of side reactions of an anode interface and a cathode interface, and on the side of the anode, the fluorine-containing diaphragm can induce the formation of a solid electrolyte interface film (SEI film) containing lithium fluoride (LiF), thereby being beneficial to interface compatibility and simultaneously reducing interface impedance; in addition, the fluorine-containing diaphragm can also play a role on the positive electrode side, and fluorine has high electronegativity, so that the oxidation resistance of the electrolyte can be improved on the positive electrode side. In combination with the above effects, the separator of the sandwich structure can improve the stability of the electrolyte/electrode interface layer, thereby improving the electrochemical properties of the lithium battery, such as the cycle performance and the like.
Drawings
In order to more clearly illustrate the examples of the application or the technical solutions of the prior art, the drawings used in the examples will be briefly described below, it being obvious that the drawings in the following description are only examples of the application and that other embodiments can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 shows cycle performance of lithium iron phosphate-based batteries using different separators in example 1 and comparative example 1.
Fig. 2 shows the charge and discharge curves of a ternary nickel cobalt manganese-based battery using a commercial Celgard separator in comparative example 2.
Fig. 3 shows the charge and discharge curves of a ternary nickel cobalt manganese-based battery using a single layer coated PVDF-HFP copolymer separator in comparative example 3.
Fig. 4 shows charge and discharge curves of a ternary nickel cobalt manganese-based battery using a lithium battery separator of the present application in example 2.
Detailed Description
The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the application are shown. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments that can be obtained by a person skilled in the art based on the embodiments of the present application are within the scope of the present application.
In the application of lithium batteries, the cycle process of the battery is usually accompanied by low Coulombic Efficiency (CE) due to continuous decomposition of electrolyte and the like, thus the service life of the battery is reduced, the popularization and application of the battery are affected, and the performance of the lithium battery diaphragm serving as one of core materials directly affects the electrochemical performances such as the discharge capacity, the cycle service life and the like of the lithium battery, so the application researches the improvement of the performance of the lithium battery from the perspective of the lithium battery diaphragm.
As known to those skilled in the art, the separator has a main function of separating the positive and negative electrodes of the battery, preventing the two electrodes from being in contact to be short-circuited, and also has a function of allowing electrolyte ions to pass through. The separator material is non-conductive, the type of battery is different, and the separator used is different. For lithium battery series, since the electrolyte is an organic solvent system, a separator material resistant to an organic solvent is required, and thus, the separator material for lithium battery market is mainly a polyolefin separator with excellent mechanical properties, chemical stability and relatively low cost, mainly comprising polyethylene and polypropylene. With the increasing demands of the terminal market for battery performance and the diversification of functional demands, separator coatings are widely used due to the great improvement of battery performance.
Therefore, based on the modification technology of the diaphragm, the application provides a novel lithium battery diaphragm with a sandwich structure and a fluorine-containing coating so as to improve the electrochemical performance of a lithium battery.
Specifically, according to a first aspect of the present application, there is provided a lithium battery separator, wherein the separator includes: the fluorine-containing coating is formed on two sides of the substrate.
In some embodiments, the fluorine-containing material in the fluorine-containing coating is polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer.
In some embodiments, the fluorine-containing coating has a thickness of 0.5 to 3 μm, e.g., 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc., preferably the thickness is 1 μm. If the thickness of the fluorine-containing coating layer is less than 0.5 μm, it is difficult to uniformly coat; if the thickness of the fluorine-containing coating layer is more than 3. Mu.m, the overall chemical activity of the separator is increased, giving an unclear effect.
In some embodiments, the substrate is polyethylene, polypropylene, polymethylpentene, nonwoven, or polyimide, or a combination thereof. Of course, other suitable substrates known to those skilled in the art to be useful for modification of lithium batteries may also be used, as the application is not limited thereto.
According to a second aspect of the present application, there is also provided a method of preparing the lithium battery separator according to the first aspect of the present application, wherein the method comprises: preparing a solution containing polyvinylidene fluoride-hexafluoropropylene copolymer as a fluorine-containing material, forming the solution into a fluorine-containing coating layer on both sides of a substrate by wet coating or electrospinning, thereby obtaining the lithium battery separator.
The lithium battery separator prepared by forming the fluorine-containing coating on the two sides of the substrate can reduce the occurrence of side reactions of an interface, so that the stability of the interface is improved, and the lithium battery separator can be used as the separator to be included in a lithium battery to improve the electrochemical performance of the lithium battery.
Thus, according to a third aspect of the present application there is provided a lithium battery comprising a lithium battery separator according to the first aspect of the present application or a lithium battery separator prepared by a method according to the second aspect of the present application.
In some embodiments, the lithium battery is a lithium metal battery. Of course, the lithium battery may be a lithium ion battery, which is not further limited in the present application.
As understood by those skilled in the art, a "lithium metal battery" refers to a battery using metallic lithium and its alloys or copper foil as a negative electrode, and a positive electrode material matched with the battery may be a commercial positive electrode material such as lithium iron phosphate, a lithium-rich ternary material, e.g., a ternary nickel cobalt manganese-based lithium-rich material.
In some embodiments, the positive electrode material of the lithium metal battery is lithium iron phosphate or ternary lithium. In some embodiments, the ternary lithium is LiNi 0.8 Co 0.1 Mn 0.1 O 2 . Of course, other positive electrode materials known to those skilled in the art to be useful in lithium batteries may be used, as the present application is not limited thereto.
In some embodiments, the negative electrode material of the lithium metal battery is a metallic lithium sheet. In some embodiments, the thickness of the metallic lithium sheet is 0.1-1mm, e.g., 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, preferably the thickness of the metallic lithium sheet is 0.5mm. If the thickness of the metal lithium sheet is lower than 0.1mm, the metal lithium sheet is close to the situation of a full battery without negative electrode lithium metal, and the N/P ratio of positive and negative electrode active substances needs to be regulated; if the thickness of the metallic lithium sheet is more than 1mm, the electrochemical properties are not greatly affected but the manufacturing cost is increased and the safety is lowered, which is generally not suitable for use in lithium batteries.
According to a fourth aspect of the present application, there is also provided the use of a lithium battery separator according to the first aspect of the present application or a lithium battery separator prepared by a method according to the second aspect of the present application in a lithium battery.
In some embodiments, the lithium battery is a lithium metal battery. Of course, the lithium battery may be a lithium ion battery, which is not further limited in the present application.
The present application prepares a new lithium battery separator in a "sandwich" structure by forming fluorine-containing coatings comprising fluorine-containing materials such as PVDF-HFP copolymer on both sides of a conventional separator such as a polypropylene separator, which has certain advantages over existing commercial separators, single-sided fluorine-containing separators, and integrally formed fluorine-containing separators. Firstly, the fluorine-containing coating can reduce the occurrence of side reactions of an anode interface and a cathode interface, and on the side of the anode, the fluorine-containing diaphragm can induce the formation of a solid electrolyte interface film (SEI film) containing lithium fluoride (LiF), thereby being beneficial to interface compatibility and simultaneously reducing interface impedance; in addition, the fluorine-containing diaphragm can also play a role on the positive electrode side, and fluorine has high electronegativity, so that the oxidation resistance of the electrolyte can be improved on the positive electrode side. In combination with the above effects, the separator of the sandwich structure can improve the stability of the electrolyte/electrode interface layer, thereby improving the electrochemical properties of the lithium battery, such as the cycle performance and the like.
The present application will now be described in more detail with reference to the drawings and examples, which are only preferred embodiments of the present application and are not intended to limit the present application. All materials and reagents of the application are materials and reagents of the conventional market unless specified otherwise.
Examples
In the present application, celgard membrane was purchased from Shenzhen friendly research technology Co., ltd, model Celgard 2325.
1. Preparation of fluorine-containing separator
Preparation example 1: preparation of the separator with double-sided fluorine-containing coating of the present application:
in the application, the preparation of the membrane with the sandwich structure is preferably carried out by using wet coating, and the preparation process can be divided into the following three steps:
(1) Dissolving PVDF-HFP copolymer in N-methyl pyrrolidone (NMP), and fully stirring to form uniform slurry;
(2) Coating the slurry on two sides of a Celgard diaphragm in a coating machine, wherein the fixed coating thickness is 1 mu m;
(3) Drying, and winding after the solvent is fully volatilized.
Preparation example 2: preparation of separator with single-sided fluorine-containing coating:
(1) Dissolving PVDF-HFP copolymer in N-methyl pyrrolidone (NMP), and fully stirring to form uniform slurry;
(2) Coating the slurry on one side of a Celgard diaphragm in a coater, wherein the fixed coating thickness is 1 mu m;
(3) Drying, and winding after the solvent is fully volatilized.
2. Assembly of lithium batteries Using the separator of the application
In the following examples of the present application, the positive electrode active material was supported at a loading of about 2mg/cm 2 。
Example 1: assembling lithium iron phosphate-based lithium battery using the lithium battery separator of the present application the double-sided coated 1 μm polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer Celgard separator prepared in preparation example 1 was used as a lithium battery separator, lithium iron phosphate was used as a positive electrode material, and a 0.5mm thick lithium sheet was used as a negative electrode to assemble a battery; then, adding 1M of lithium bis (trifluoromethyl) sulfonyl imide (LiTFSI) into a solution of fluoroethylene carbonate (FEC), ethylene glycol dimethyl ether (DME) and Dioxolane (DOL) according to the volume ratio of 1:2:7 to be used as an electrolyte; finally, it is left at 60℃for 12 hours to perform in-situ polymerization (reaction of in-situ polymerization is shown by the following formula (I)) to form a semi-solid electrolyte, thereby completing the assembly of the lithium battery.
Example 2: liNi using the lithium battery separator of the present application 0.8 Co 0.1 Mn 0.1 O 2 Assembly of lithium-based batteries
Celgard separator coated with 1 μm PVDF-HFP copolymer on both sides prepared in preparation example 1 was used as lithium battery separator, liNi 0.8 Co 0.1 Mn 0.1 0 2 The method comprises the steps of (1) taking a lithium sheet with the thickness of 0.5mm as a cathode material to assemble a battery; then, 1.2M LiPF was added 6 The electrolyte is prepared from Ethyl Carbonate (EC) and Ethyl Methyl Carbonate (EMC) according to a volume ratio of 3:7; finally, the mixture is left to stand at 60 ℃ for 12 hours to carry out in-situ polymerization, and the polymerization is carried outThe EC ring-opening reaction generates ethylene carbonate chains and ethylene oxide chains, thereby forming a semi-solid electrolyte; thereby completing the assembly of the lithium battery.
3. Assembly of lithium batteries with commercial Celgard separator and single-sided coated fluorine-containing separator
In the following comparative examples of the present application, the positive electrode active material was supported at about 2mg/cm 2 。
Comparative example 1: assembly of lithium iron phosphate based lithium batteries using commercial Celgard separators
The lithium battery was assembled with a commercial Celgard-containing separator as the lithium battery separator for electrochemical testing. In the assembly process, lithium iron phosphate is taken as an anode, a 0.5mm lithium sheet is taken as a cathode, 1M LiTFSI solution with the volume ratio of 1:2:7 is added to FEC, DME, DOL as electrolyte, and the battery is placed for 12 hours at 60 ℃ after being packaged.
Comparative example 2: liNi using commercial Celgard diaphragm 0.8 Co 0.1 Mn 0.1 O 2 Assembly of lithium-based batteries
The commercial Celgard-containing diaphragm is used as a lithium battery diaphragm, and a lithium ion battery is assembled for electrochemical testing. In the assembly process, liNi is used 0.8 Co 0.1 Mn 0.1 0 2 For positive electrode, 0.5mm lithium sheet was used as negative electrode, and 1.2M LiPF was added 6 And taking the solution of EC and EMC according to the volume ratio of 3:7 as electrolyte, packaging the battery, and standing at 60 ℃ for 12h.
Comparative example 3: liNi using single-sided coated PVDF-HFP copolymer separator 0.8 Co 0.1 Mn 0.1 O 2 Assembly of lithium-based batteries
Celgard separator coated with PVDF-HFP copolymer on one side prepared in preparation example 2 was used as lithium battery separator (with fluorine-containing coating facing negative electrode), and LiNi was used 0.8 Co 0.1 Mn 0.1 O 2 As a positive electrode material, a lithium sheet with the thickness of 0.5mm is used as a negative electrode to assemble a battery; then, 1.2M LiPF was added 6 The electrolyte is prepared from EC and EMC in a volume ratio of 3:7; finally, standing at 60 ℃ for 12 hours to perform in-situ polymerization, wherein during the polymerization, EC ring-opening reaction generates ethylene carbonate chains and ethylene oxide chains, thereby formingA semi-solid electrolyte; thereby completing the assembly of the lithium battery.
4. Electrochemical performance test
The testing method comprises the following steps:
the lithium batteries prepared in examples 1-2 and comparative examples 1-3 were subjected to electrochemical tests as follows:
cycle performance test and charge-discharge test: the test is carried out at 30 ℃, the cut-off voltage of the lithium iron phosphate test is 2.5-4.0V, and the cut-off voltage of the ternary lithium nickel manganese oxide test is 2.7-4.3V. Performing constant-current charge and discharge circulation for 3 cycles at a current multiplying power of 0.1C to serve as an activation process of the battery; after that, a cycle stability test was performed at a current magnification of 1C.
Test results:
fig. 1 shows cycle performance of lithium iron phosphate-based batteries using different separators in example 1 and comparative example 1. As can be seen from fig. 1, the initial capacity of the battery including the separator of the present application at 1C was 144mAh/g, and the coulombic efficiency was as high as 99.7%. The high capacity retention of 86% after 1000 cycles is still demonstrated, indicating that the presence of a stable electrolyte/electrode interface inside the cell, in particular the interface between the positive electrode and the electrolyte, exhibits excellent stability. In contrast, in comparative example 1, the cell containing the commercial Celgard separator was unstable with increasing number of cycles, which rapidly decreased in capacity after 600 cycles until the cell failed. Therefore, the membrane with the sandwich structure can improve the interface stability of the lithium battery, thereby improving the cycle stability of the battery.
Fig. 2, 3, and 4 show charge and discharge curves of the ternary nickel-cobalt manganese-based batteries in comparative example 2, comparative example 3, and example 2, respectively. In FIG. 2, the battery of comparative example 2 had a first charge capacity of 228mAh/g, a reversible discharge capacity of 192mAh/g, and a first coulombic efficiency of 84.2%. In FIG. 3, the battery of comparative example 3 had a first charge capacity of 233mAh/g, a reversible discharge capacity of 205mAh/g, and a first coulombic efficiency of 88%. In fig. 4, the battery of example 2 had a first charge capacity of 234mAh/g, a reversible capacity of 211mAh/g, and a first coulombic efficiency of 90.2%.
As can be seen from fig. 2 and 4, the first coulombic efficiency of the lithium battery using the double-sided coated fluorine-containing separator in example 2 is significantly higher than that of the lithium battery using the commercial Celgard separator in comparative example 2, and this difference is caused by the unique stability of the interface layer between the fluorine-containing separator and the electrode of the "sandwich" structure provided by the present application, which can reduce the occurrence of interface side reactions, thereby improving the stability of the interface.
As can be seen from fig. 3 and 4, the lithium battery using the double-sided coated "sandwich" structure fluorine-containing separator in example 2 was superior to the lithium battery using the single-sided coated fluorine-containing separator in comparative example 3, which demonstrates that PVDF-HFP copolymer did improve the positive electrode side interface.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application.
Claims (10)
1. A lithium battery separator, wherein the separator comprises:
a substrate, and
and the fluorine-containing coating is formed on two sides of the substrate.
2. The lithium battery separator of claim 1, wherein the fluorine-containing material in the fluorine-containing coating is polyvinylidene fluoride-hexafluoropropylene copolymer.
3. The lithium battery separator according to any of claims 1-2, wherein the fluorine-containing coating has a thickness of 0.5-3 μιη, preferably the thickness is 1 μιη.
4. The lithium battery separator of any of claims 1-3, wherein the substrate is polyethylene, polypropylene, polymethylpentene, nonwoven, or polyimide, or a combination thereof.
5. A method of making the lithium battery separator of any of claims 1-4, wherein the method comprises: preparing a solution containing polyvinylidene fluoride-hexafluoropropylene copolymer as a fluorine-containing material, forming the solution into a fluorine-containing coating layer on both sides of a substrate by wet coating or electrospinning, thereby obtaining the lithium battery separator.
6. A lithium battery, wherein the lithium battery comprises the lithium battery separator of any one of claims 1-4 or the lithium battery separator prepared by the method of claim 5.
7. The lithium battery of claim 6, wherein the positive electrode material of the lithium battery is a lithium iron phosphate, ternary nickel cobalt manganese-based lithium-rich material.
8. The lithium battery of any of claims 6-7, wherein the lithium battery is a lithium metal battery.
9. Use of a lithium battery separator according to any one of claims 1-4 or a lithium battery separator prepared by the method of claim 5 in a lithium battery.
10. The use of claim 9, wherein the lithium battery is a lithium metal battery.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US202263314480P | 2022-02-28 | 2022-02-28 | |
| US63/314,480 | 2022-02-28 |
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| CN116666907A true CN116666907A (en) | 2023-08-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310170567.2A Pending CN116666907A (en) | 2022-02-28 | 2023-02-27 | Lithium battery diaphragm, preparation method thereof, lithium battery comprising lithium battery diaphragm and application of lithium battery diaphragm |
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| Country | Link |
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| CN (1) | CN116666907A (en) |
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- 2023-02-27 CN CN202310170567.2A patent/CN116666907A/en active Pending
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