CN116207370A - High-performance SEI film and preparation method thereof - Google Patents
High-performance SEI film and preparation method thereof Download PDFInfo
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- CN116207370A CN116207370A CN202310500335.9A CN202310500335A CN116207370A CN 116207370 A CN116207370 A CN 116207370A CN 202310500335 A CN202310500335 A CN 202310500335A CN 116207370 A CN116207370 A CN 116207370A
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- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 58
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 55
- 239000011593 sulfur Substances 0.000 claims abstract description 55
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 54
- 238000003756 stirring Methods 0.000 claims abstract description 48
- 239000006258 conductive agent Substances 0.000 claims abstract description 26
- 239000002904 solvent Substances 0.000 claims abstract description 26
- 239000011230 binding agent Substances 0.000 claims abstract description 25
- 239000011267 electrode slurry Substances 0.000 claims abstract description 25
- 238000002156 mixing Methods 0.000 claims abstract description 21
- 239000003792 electrolyte Substances 0.000 claims abstract description 15
- 238000000227 grinding Methods 0.000 claims abstract description 15
- 239000011248 coating agent Substances 0.000 claims abstract description 12
- 238000000576 coating method Methods 0.000 claims abstract description 12
- 238000007731 hot pressing Methods 0.000 claims abstract description 12
- 238000005096 rolling process Methods 0.000 claims abstract description 12
- 238000003466 welding Methods 0.000 claims abstract description 12
- 238000004804 winding Methods 0.000 claims abstract description 12
- 239000000126 substance Substances 0.000 claims abstract description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 20
- 239000002033 PVDF binder Substances 0.000 claims description 20
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 6
- 239000006230 acetylene black Substances 0.000 claims description 6
- 239000004917 carbon fiber Substances 0.000 claims description 6
- 239000002041 carbon nanotube Substances 0.000 claims description 6
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- 229910052744 lithium Inorganic materials 0.000 claims description 3
- 229910018091 Li 2 S Inorganic materials 0.000 claims description 2
- 238000009775 high-speed stirring Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 239000005077 polysulfide Substances 0.000 claims description 2
- 229920001021 polysulfide Polymers 0.000 claims description 2
- 150000008117 polysulfides Polymers 0.000 claims description 2
- 239000000654 additive Substances 0.000 description 9
- 230000000996 additive effect Effects 0.000 description 8
- 239000006229 carbon black Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- -1 alkyl lithium sulfate salt Chemical compound 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 229910018068 Li 2 O Inorganic materials 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000013538 functional additive Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000003786 synthesis reaction 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
-
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a high-performance SEI film and a preparation method thereof, wherein the preparation method comprises the following steps: s1, mixing lithium iron phosphate with sulfur-containing substances, and grinding at high temperature to obtain sulfur-coated lithium iron phosphate; s2, stirring the sulfur-coated lithium iron phosphate for 5-10min, adding the binder and the conductive agent, continuing stirring for 15-20min, adding the solvent, continuing stirring for 15-20min, then placing in a vacuum environment, stirring for 3-5h at a high speed, and defoaming after viscosity adjustment to obtain positive electrode slurry; s3, coating the obtained positive electrode slurry on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to obtain a battery cell; s4, injecting the electrolyte into the battery core, and standing for 24-48 hours at 40-50 ℃ to obtain the high-performance SEI film. The SEI film with high performance prepared by the invention has better stability and dynamic performance.
Description
Technical Field
The invention relates to an SEI film, in particular to a high-performance SEI film and a preparation method thereof.
Background
Li 2 CO 3 、Li 2 SO 4 LiOH, liF, etc. are considered to be important components of the SEI film, and play a role in electronic insulation. At present, there are two main approaches to constructing SEI films: (1) adding functional additives: the film-forming additive mainly comprises unsaturated ester additive (VC, FEC), sulfur-containing additive (PS, DTD), lithium salt additive (LIBOB, liPO) 2 F 2 ) Inorganic compound additive (Na 2 CO 3 、Na 2 SO 3 ) Etc.; (2) constructing an artificial SEI film. The SEI film consumes part of lithium ions, reduces the charge and discharge efficiency of the electrode material, can effectively prevent the intercalation of solvent molecules, avoid damaging the electrode material, and improve the service life and cycle performance of the battery, so that the SEI film has a critical influence on the performance of the electrode material, and therefore, the development of a high-performance SEI interface film with practicability and universality becomes one of research hot spots in the industry.
At present, related patents of SEI films in the field of lithium ion batteries mainly include: (1) Starting from the anode plate aspect, such as the Chinese patent with publication number of CN 102610774B; (2) Constructed from the chemical process, such as the chinese patent publication No. CN110034336 a. These patents are studied and implemented mainly by businesses and schools.
Problems with existing SEI films include: film forming additives such as carbonate matrix systems are prone to decomposition to produce gases, and have poor electrochemical properties at high temperatures, which can negatively impact the thermal and safety performance of the battery; the sulfur-containing additive has the characteristics that the valence state of sulfur is inconsistent, and a general reduction mechanism is not available, so that the synthesis process is complex, the cost is high, and the sulfur-containing additive is difficult to widely use at present; construction of artificial SEI has been studied more, but the current system is difficultTo satisfy both mechanical flexibility and rapid Li + The need for conduction; the SEI film with high performance constructed by improving the formation process consumes longer time in the practical application process, and the SEI film is not beneficial to production and implementation because batteries with different types need to be verified independently.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method of a high-performance SEI film, and the high-performance SEI film prepared by the preparation method has better stability and dynamic performance.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a preparation method of a high-performance SEI film comprises the following steps:
s1, mixing lithium iron phosphate with sulfur-containing substances, and grinding for 10-20min at 70-100 ℃ to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 5-10min, adding a binder and a conductive agent, continuing stirring for 15-20min, adding a solvent, continuing stirring for 15-20min, then placing in a vacuum environment, stirring for 3-5h at a high speed, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 24-48 hours at the temperature of 40-50 ℃ to obtain the high-performance SEI film.
Further, in the step S1, the mass ratio of the lithium iron phosphate to the sulfur content is (99-199) 1.
Further, in the step S1 of the present invention, the sulfur-containing material is elemental sulfur or lithium polysulfide Li 2 S x X is a natural number of 1-8.
Further, in the step S1, the rotating speed during grinding is 10-20r/min.
Further, in the step S2, the mass ratio of the sulfur coated lithium iron phosphate, the binder, the conductive agent and the solvent is (95-97): 2-4): 1-3): 100.
Further, in step S2 of the present invention, the binder is PVDF.
Further, in the step S2 of the present invention, the conductive agent is one of acetylene black, carbon fiber or carbon nanotube.
Further, in the step S2 of the present invention, the solvent is N-methylpyrrolidone.
Further, in the step S2, the high-speed stirring speed is 800-1000r/min.
The invention also provides the high-performance SEI film obtained by the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention mixes sulfur-containing material and lithium iron phosphate by heating and grinding mode to make the sulfur-containing material uniformly cover the surface of lithium iron phosphate, then according to the prior art prepares the lithium iron phosphate covered with sulfur-containing material, adhesive and conductive agent into positive electrode slurry, then makes positive electrode plate and negative electrode plate into electric core, after injecting electrolyte, a portion of sulfur-containing material can produce alkyl lithium sulfate salt (refer to reaction formula I) by oxidation reaction, and can be diffused into anode, and form firm and thin SEI film on the surface of anode, and the alkyl lithium sulfate salt (R-SO 3 Li), the SEI film constructed has good elasticity, can adapt to huge volume change, and can inhibit repeated cracking and continuous growth, so that the SEI film has good stability; the other part of the sulfur-containing compound is directly diffused to the anode side and reacts with methyl ethyl carbonate (EMC), ethylene Carbonate (EC) and the like in the electrolyte (refer to the second reaction formula) to produce the epoxy compound, thereby increasing Li + A transmission channel capable of forming a conductive network to rapidly transmit Li + Thereby improving the dynamic performance of the battery cell;
reactive one
Reactive type II
2. The composition of the conventional SEI film mainly includes various inorganic components such as Li 2 CO 3 、LiF、Li 2 O, liOH, etc., the decomposition temperature of which is lower than that of the lithium alkyl phosphate, so that the sulfur-containing SEI film prepared by the invention has higher decomposition temperature and is safer for the overall performance of the battery cell; in addition, the sulfur-containing SEI film prepared by the invention can also effectively improve the cycling stability of the battery under high voltage in the cycling process;
3. compared with the thought of using sulfur-containing additive electrolyte, the method has the advantages of simpler process, lower cost, easier popularization and use and compatible effect on various systems.
Detailed Description
The present invention will be described in detail with reference to specific examples, wherein the exemplary embodiments and descriptions of the present invention are provided for the purpose of illustration and are not intended to be limiting.
Example 1 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with elemental sulfur S according to a mass ratio of 199:1 8 Mixing, grinding for 15min at the temperature of 80 ℃ at the rotating speed of 15r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 8min, adding a binder PVDF and a conductive agent acetylene black, continuing stirring for 16min, adding a solvent N-methylpyrrolidone, continuing stirring for 16min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent acetylene black to the solvent N-methylpyrrolidone is 96:3:2:100, then placing in a vacuum environment, stirring for 4h at a high speed of 900r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing at 45 ℃ for 36h to obtain the high-performance SEI film.
Example 2 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 99:1 2 S, mixing, grinding for 15min at 80 ℃ at the rotating speed of 10r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 5min, adding a binder PVDF and a conductive agent carbon black, continuing stirring for 15min, adding a solvent N-methylpyrrolidone, continuing stirring for 15min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon black to the solvent N-methylpyrrolidone is 95:2:1:100, then placing in a vacuum environment, stirring for 5h at a high speed of 800r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing at 40 ℃ for 48 hours to obtain the high-performance SEI film.
Example 3 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 150:1 2 S 2 Mixing, grinding for 20min at the temperature of 70 ℃ at the rotating speed of 20r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 10min, adding a binder PVDF and a conductive agent carbon fiber, continuing stirring for 20min, adding a solvent N-methylpyrrolidone, continuing stirring for 20min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon fiber to the solvent N-methylpyrrolidone is 97:4:3:100, then placing in a vacuum environment, stirring at a high speed for 5h under 1000r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 24 hours at 50 ℃ to obtain the high-performance SEI film.
Example 4 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 120:1 2 S 3 Mixing, grinding for 10min at the temperature of 100 ℃ at the rotating speed of 15r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 9min, adding a binder PVDF and a conductive agent carbon nanotube, continuing stirring for 18min, adding a solvent N-methylpyrrolidone, continuing stirring for 18min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon nanotube to the solvent N-methylpyrrolidone is 96:3:1:100, then placing in a vacuum environment, stirring for 4h at a high speed at 900r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 30 hours at 45 ℃ to obtain the high-performance SEI film.
Example 5 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 100:1 2 S 4 Mixing, grinding for 12min at 90 ℃ at a rotating speed of 10r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 6min, adding a binder PVDF and a conductive agent carbon fiber, continuing stirring for 17min, adding a solvent N-methylpyrrolidone, continuing stirring for 17min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon fiber to the solvent N-methylpyrrolidone is 96:1:1:100, then placing in a vacuum environment, stirring for 4h at a high speed at 900r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 40 hours at 45 ℃ to obtain the high-performance SEI film.
Example 6a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 140:1 2 S 5 Mixing, grinding for 18min at the temperature of 75 ℃ at the rotating speed of 20r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 9min, adding a binder PVDF and a conductive agent carbon black, continuing stirring for 19min, adding a solvent N-methylpyrrolidone, continuing stirring for 19min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon black to the solvent N-methylpyrrolidone is 97:4:2:100, then placing in a vacuum environment, stirring for 5h at a high speed of 800r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing at 40 ℃ for 48 hours to obtain the high-performance SEI film.
Example 7 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 160:1 2 S 6 Mixing, grinding for 16min at the temperature of 85 ℃ at the rotating speed of 20r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 10min, adding a binder PVDF and a conductive agent acetylene black, continuing stirring for 20min, adding a solvent N-methylpyrrolidone, continuing stirring for 20min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent acetylene black to the solvent N-methylpyrrolidone is 95:2:2:100, then placing in a vacuum environment, stirring for 3h at a high speed of 1000r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing at 40 ℃ for 36h to obtain the high-performance SEI film.
Example 8 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 120:1 2 S 7 Mixing, grinding for 14min at the temperature of 95 ℃ at the rotating speed of 15r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 8min, adding a binder PVDF and a conductive agent carbon nanotube, continuing stirring for 15min, adding a solvent N-methylpyrrolidone, continuing stirring for 15min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon nanotube to the solvent N-methylpyrrolidone is 97:3:1:100, then placing in a vacuum environment, stirring at a high speed for 3.5h under 1000r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 24 hours at 50 ℃ to obtain the high-performance SEI film.
Example 9 a high performance SEI film was prepared according to the following steps:
s1, mixing lithium iron phosphate with Li according to a mass ratio of 180:1 2 S 8 Mixing, grinding for 12min at 90 ℃ at a rotating speed of 10r/min to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 7min, adding a binder PVDF and a conductive agent carbon black, continuing stirring for 16min, adding a solvent N-methylpyrrolidone, continuing stirring for 16min, wherein the mass ratio of the sulfur-coated lithium iron phosphate to the binder PVDF to the conductive agent carbon black to the solvent N-methylpyrrolidone is 95:2:2:100, then placing in a vacuum environment, stirring at a high speed for 5h at 800r/min, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 30 hours at 50 ℃ to obtain the high-performance SEI film.
Comparative example: the difference from example 1 is only that step S1 is not included, and the sulfur-coated lithium iron phosphate in step 2 is replaced with untreated lithium iron phosphate.
Experimental example: performance testing
The battery cells prepared in examples 1-9 and the battery cells prepared in comparative examples are activated, capacity loss is tested after activation is completed, and test results show that examples 1-9 have almost no capacity loss, and the irreversible capacity loss of the high-performance SEI film prepared by the invention is less and the stability is better.
The battery core prepared in the example 1 and the battery core prepared in the comparative example are activated, and the multiplying power performance is tested respectively after the activation is completed, and the test result shows that the multiplying power performance of the example 1 is improved by about 13.1% compared with the comparative example, so that the dynamic performance of the high-performance SEI film is improved.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (10)
1. A preparation method of a high-performance SEI film is characterized by comprising the following steps: the method comprises the following steps:
s1, mixing lithium iron phosphate with sulfur-containing substances, and grinding for 10-20min at 70-100 ℃ to obtain sulfur-coated lithium iron phosphate;
s2, stirring the sulfur-coated lithium iron phosphate obtained in the step S1 for 5-10min, adding a binder and a conductive agent, continuing stirring for 15-20min, adding a solvent, continuing stirring for 15-20min, then placing in a vacuum environment, stirring for 3-5h at a high speed, and defoaming after viscosity adjustment to obtain positive electrode slurry;
s3, coating the positive electrode slurry obtained in the step S2 on a positive electrode plate, rolling the positive electrode plate, winding the positive electrode plate, a negative electrode plate and a diaphragm, hot-pressing, welding a lug top cover, putting into a shell, and baking to prepare a battery cell;
s4, injecting the electrolyte into the battery cell obtained in the step S3, and standing for 24-48 hours at the temperature of 40-50 ℃ to obtain the high-performance SEI film.
2. The method for preparing a high-performance SEI film according to claim 1, wherein: in the step S1, the mass ratio of the lithium iron phosphate to the sulfur content is (99-199) 1.
3. The method for preparing a high-performance SEI film according to claim 2, wherein: in the step S1, the sulfur-containing compound is elemental sulfur or lithium polysulfide Li 2 S x X is a natural number of 1-8.
4. The method for preparing a high-performance SEI film according to claim 1, wherein: in the step S1, the rotating speed during grinding is 10-20r/min.
5. The method for preparing a high-performance SEI film according to claim 1, wherein: in the step S2, the mass ratio of the sulfur-coated lithium iron phosphate, the binder, the conductive agent and the solvent is (95-97): 2-4): 1-3): 100.
6. The method for preparing a high-performance SEI film according to claim 5, wherein: in the step S2, the binder is PVDF.
7. The method for preparing a high-performance SEI film according to claim 5, wherein: in the step S2, the conductive agent is one of acetylene black, carbon fiber or carbon nanotube.
8. The method for preparing a high-performance SEI film according to claim 5, wherein: in the step S2, the solvent is N-methyl pyrrolidone.
9. The method for preparing a high-performance SEI film according to claim 1, wherein: in the step S2, the high-speed stirring speed is 800-1000r/min.
10. The high performance SEI film obtained by the production method according to any one of claims 1 to 9.
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