CN113659280A - Composite coating diaphragm with high conductivity, preparation method thereof and lithium battery formed by assembling composite coating diaphragm - Google Patents
Composite coating diaphragm with high conductivity, preparation method thereof and lithium battery formed by assembling composite coating diaphragm Download PDFInfo
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- CN113659280A CN113659280A CN202110790180.8A CN202110790180A CN113659280A CN 113659280 A CN113659280 A CN 113659280A CN 202110790180 A CN202110790180 A CN 202110790180A CN 113659280 A CN113659280 A CN 113659280A
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- 239000011248 coating agent Substances 0.000 title claims abstract description 75
- 238000000576 coating method Methods 0.000 title claims abstract description 75
- 239000002131 composite material Substances 0.000 title claims abstract description 57
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 39
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- -1 polyethylene Polymers 0.000 claims abstract description 35
- 239000000463 material Substances 0.000 claims abstract description 31
- 150000002484 inorganic compounds Chemical class 0.000 claims abstract description 26
- 229910010272 inorganic material Inorganic materials 0.000 claims abstract description 26
- 239000011230 binding agent Substances 0.000 claims abstract description 25
- 239000004698 Polyethylene Substances 0.000 claims abstract description 23
- 239000003960 organic solvent Substances 0.000 claims abstract description 23
- 229920000573 polyethylene Polymers 0.000 claims abstract description 23
- 239000002002 slurry Substances 0.000 claims abstract description 23
- 230000020477 pH reduction Effects 0.000 claims abstract description 17
- 239000008367 deionised water Substances 0.000 claims abstract description 16
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 13
- 239000002270 dispersing agent Substances 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 13
- 239000003792 electrolyte Substances 0.000 claims abstract description 9
- 239000000843 powder Substances 0.000 claims description 28
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 14
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 14
- 239000002033 PVDF binder Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 11
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 claims description 9
- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 claims description 9
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 claims description 9
- 239000007864 aqueous solution Substances 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 8
- 239000006185 dispersion Substances 0.000 claims description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 5
- 238000007756 gravure coating Methods 0.000 claims description 5
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 5
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- 229920006184 cellulose methylcellulose Polymers 0.000 claims description 4
- GBCAVSYHPPARHX-UHFFFAOYSA-M n'-cyclohexyl-n-[2-(4-methylmorpholin-4-ium-4-yl)ethyl]methanediimine;4-methylbenzenesulfonate Chemical compound CC1=CC=C(S([O-])(=O)=O)C=C1.C1CCCCC1N=C=NCC[N+]1(C)CCOCC1 GBCAVSYHPPARHX-UHFFFAOYSA-M 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000000243 solution Substances 0.000 claims description 3
- 239000002202 Polyethylene glycol Substances 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- 229920001223 polyethylene glycol Polymers 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 2
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 13
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 12
- 230000014759 maintenance of location Effects 0.000 abstract description 6
- 230000002035 prolonged effect Effects 0.000 abstract description 3
- 230000002950 deficient Effects 0.000 abstract description 2
- 238000003756 stirring Methods 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 19
- 239000007788 liquid Substances 0.000 description 7
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 6
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 229920003048 styrene butadiene rubber Polymers 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
- 239000002174 Styrene-butadiene Substances 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 238000005034 decoration Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000003487 electrochemical reaction Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- 239000004816 latex Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 239000005416 organic matter Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- FGHSTPNOXKDLKU-UHFFFAOYSA-N nitric acid;hydrate Chemical compound O.O[N+]([O-])=O FGHSTPNOXKDLKU-UHFFFAOYSA-N 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- 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
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/497—Ionic conductivity
-
- 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 discloses a composite coating diaphragm with high conductivity, a preparation method thereof and a lithium battery formed by assembling the same, wherein the preparation method comprises the following steps: step 1: acidizing the polyethylene base film; step 2: dispersing an inorganic compound, a dispersant and an organic solvent uniformly, adding a cross-linking agent, and mixing uniformly to obtain a mixed material 1; dispersing the mixed binder in deionized water to obtain a mixed material 2; uniformly mixing lithium siloxane, the mixed material 1 and the mixed material 2 to prepare composite coating diaphragm slurry; and step 3: and coating the obtained composite coating diaphragm slurry on one side or two sides of the polyethylene base film subjected to acidification treatment, and drying to obtain the composite coating diaphragm with high conductivity. Lithium siloxane in the prepared composite coating diaphragm can release lithium ions, and the conductivity is obviously increased. When the lithium battery is applied to the lithium battery, the lithium ion deficient in the electrolyte can be supplemented, so that the capacity retention rate of the lithium battery is higher, the electrochemical performance of the lithium battery is improved, and the service life of the lithium battery is prolonged.
Description
Technical Field
The invention relates to the technical field of lithium battery diaphragms, in particular to a composite coating diaphragm with high conductivity, a preparation method of the composite coating diaphragm and a lithium battery formed by assembling the composite coating diaphragm.
Background
The lithium ion battery is widely applied due to excellent electrochemical performance, particularly, with the rapid development of new energy industry, the lithium battery is more and more applied to a power automobile, but the key of the electrochemical performance of the power lithium ion battery is that when the power lithium ion battery is charged and discharged for the first time, a Solid Electrolyte Interface (SEI) film is generated between a diaphragm and a negative electrode, so that part of lithium ions are obviously consumed, irreversible loss of the lithium ions of a positive electrode material is caused, the capacity of the battery is reduced, and the first efficiency is reduced. Meanwhile, in the subsequent battery cycle process, lithium ions are continuously consumed due to various side reactions, which causes the continuous reduction of the battery performance.
The separator is one of important materials of the lithium battery, the conductivity of the separator is good or bad, the electrochemical performance of the lithium battery is seriously affected, the current market mainly tends to use a coating separator as a main material, however, the coating separator in the market has low conductivity of the produced product due to the problems of process and cost without special treatment, and as a result, the performance control of the lithium battery becomes complicated, so that the development of the coating separator with low cost and good conductivity becomes a problem which needs to be solved at present.
Disclosure of Invention
The invention aims to provide a composite coating diaphragm with high conductive performance aiming at the technical defect of low diaphragm conductivity in the prior art.
The invention also aims to provide a preparation method of the composite coating diaphragm with high conductive performance.
The invention also aims to provide a lithium battery formed by assembling the composite coating diaphragm with high conductive performance.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a preparation method of a composite coating diaphragm with high conductivity comprises the following steps:
step 1: base film acidification treatment
Soaking the polyethylene base film in acid liquor for acidification treatment, then cleaning the surface of the polyethylene base film by using deionized water, and drying for later use; the acid solution is hydrochloric acid aqueous solution, nitric acid aqueous solution or sulfuric acid aqueous solution; the concentration of the acid liquor is 1-20%.
Step 2: preparation of composite coating diaphragm slurry
Adding an inorganic compound and a dispersant into an organic solvent for uniform dispersion, adding a bis-diazacyclo cross-linking agent, and uniformly mixing to obtain a mixed material 1; the inorganic compound comprises micron alumina powder, nanometer alumina powder, micron aluminum nitride powder and nanometer aluminum nitride powder; the mass part ratio of the micron alumina powder, the nanometer alumina powder, the micron aluminum nitride powder and the nanometer aluminum nitride powder is (5.5-6.0): (0.3-0.5): (9.5-10.0): (0.8-1.0). The dispersing agent comprises one or a mixture of polyethylene glycol, polyvinyl alcohol and polyvinylpyrrolidone in any proportion; the organic solvent comprises one or a mixture of isopropanol, normal propanol and propylene glycol in any proportion; the mass part ratio of the inorganic compound to the organic solvent is (6-7.5): 8; the mass of the dispersant is 5-10% of the total mass of the inorganic compound and the organic solvent; the mass of the bis-diazacyclo cross-linking agent is 0.5-1.0% of the total mass of the inorganic compound and the organic solvent.
Dispersing the mixed binder in deionized water to obtain a mixed material 2; the mixed binder is a mixture of PVDF, sodium polyacrylate and CMC; in the mixed binder, the mass part ratio of PVDF, sodium polyacrylate and CMC is (4.5-5): (1.5-2): (5.5-6); the proportion of the total mass of the PVDF, the sodium polyacrylate and the CMC to the mass of the deionized water is 1: (18-20).
Mixing lithium siloxane, a mixed material 1 and a mixed material 2 according to a mass fraction ratio (0.3-0.5): (2-3): 7, uniformly mixing to prepare composite coating diaphragm slurry;
and step 3: film production
And (3) coating the composite coating diaphragm slurry obtained in the step (2) on one side or two sides of the polyethylene base film subjected to acidification treatment in the step (1), and drying to obtain the composite coating diaphragm with high conductivity. The coating mode is gravure coating, and the coating speed is 20-25 m/min; the drying temperature is 55-70 ℃; the coating thickness is 2.0-3.0 μm.
On the other hand, the composite coating diaphragm with high conductivity is prepared by applying the preparation method.
In another aspect of the present invention, a lithium battery includes a positive electrode, a negative electrode, an electrolyte, and the above composite coated separator having high conductive properties. The positive electrode material is a ternary material (NCM523) (purchased from Union solid Li new materials), the negative electrode material is graphite (fibrate-rubicin), the solute of the electrolyte is LiPF6 (the solvent is a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate), and the semi-cell is assembled by EC: DMC ═ 1:1 by mass). The cathode is formed by mixing graphite, a conductive agent (Keqin carbon black) and a binder SBR (styrene butadiene rubber latex) (Shenzhen Yitong) according to a mass ratio of 8:0.8:1.2, and the anode is formed by mixing a cathode material, conductive carbon black (Shenzhen Kezhida) and a binder PVDF (Chengdu Kelong) according to a mass ratio of 8:1: 1.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the composite coating diaphragm with high conductivity, lithium siloxane contained in the composite coating can release lithium ions, and the conductivity is remarkably increased. When the lithium battery is applied to the lithium battery, the lithium ion deficient in the electrolyte can be supplemented, so that the capacity retention rate of the lithium battery is higher, the electrochemical performance of the lithium battery is improved, and the service life of the lithium battery is prolonged.
2. The preparation method of the composite coating diaphragm with high conductivity provided by the invention comprises the steps of firstly, carrying out acidification treatment on the polyethylene base film, improving the chemical bond energy on the surface of an organic matter, exciting the activation sites on the surface of the diaphragm, increasing the adhesion of lithium ions, and preparing for the subsequent electrochemical reaction.
3. According to the preparation method of the composite coating diaphragm with high conductivity, provided by the invention, the mixed binder is used, and the molecular chain functional groups in the mixed binder are in interval chain distribution, so that the existence of steric hindrance is caused, the cross-linking among molecular chains is effectively inhibited, the mobility of the molecular chains is improved, and the ion conduction rate is improved.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A preparation method of a composite coating diaphragm with high conductivity comprises the following steps:
step 1: base film acidification treatment
Soaking the polyethylene base film in a nitric acid water solution with the mass concentration of 5%, acidizing the polyethylene base film, cleaning the surface of the polyethylene base film by using deionized water, and drying for later use;
step 2: preparation of composite coating diaphragm slurry
Firstly, adding an inorganic compound and a dispersing agent into an organic solvent isopropanol, dispersing for 40min at a dispersing speed of 1200rpm, and stirring for 130min at a stirring speed of 2000 rpm; wherein the inorganic compound comprises 5.5 parts of micron alumina powder, 0.3 part of nano alumina powder, 9.5 parts of micron aluminum nitride powder and 0.8 part of nano aluminum nitride powder according to the mass part ratio; the mass ratio of the inorganic compound to the organic solvent is 6: 8; the mass of the dispersing agent is 5% of the total mass of the inorganic compound and the organic solvent; then, adding a bis-diazacyclo cross-linking agent, and stirring at a stirring speed of 1800rpm for 40min to obtain a mixed material 1; wherein the mass of the cross-linking agent is 0.5 percent of the total mass of the inorganic compound and the organic solvent;
dispersing the mixed binder in deionized water, dispersing for 40min at a dispersion speed of 1500rpm, and stirring for 40min at a stirring speed of 1800rpm to obtain a mixed material 2; wherein the mass ratio of the mixed binder to the deionized water is 1: 18; the mixed binder comprises, by mass, 4.5 parts of PVDF, 1.5 parts of sodium polyacrylate and 5.5 parts of CMC;
uniformly mixing lithium siloxane, the mixed material 1 and the mixed material 2 according to the mass ratio of 0.3:2:7, and stirring at the stirring speed of 2000rpm for 35min to prepare composite coating diaphragm slurry;
and step 3: film production
Firstly, coating the composite coating diaphragm slurry obtained in the step 2 on one side of the polyethylene base film subjected to acidification treatment in the step 1 in a gravure coating mode, wherein the coating speed is 20 m/min; and fully drying at the temperature of 55 ℃ to obtain the composite coating diaphragm with the single-side coating thickness of 2.0 mu m and high conductive performance.
Comparative example 1
Compared with the example 1, the polyethylene-based film used in the comparative example is not subjected to the acidification treatment in the step 1, and the preparation method of the composite coating diaphragm slurry in the step 2 and the film preparation method in the step 3 are consistent with those in the example 1.
Example 2
A preparation method of a composite coating diaphragm with high conductivity comprises the following steps:
step 1: base film acidification treatment
Coating a nitric acid aqueous solution with the mass concentration of 8% on the surface of the polyethylene base film, acidizing the polyethylene base film, cleaning the surface of the polyethylene base film by using deionized water, and drying for later use;
step 2: preparation of composite coating diaphragm slurry
Firstly, adding an inorganic compound and a dispersing agent into an organic solvent, namely n-propanol, dispersing for 43min at a dispersion speed of 1300rpm, and stirring for 150min at a stirring speed of 2300 rpm; wherein the inorganic compound comprises 5.7 parts of micron alumina powder, 0.4 part of nano alumina powder, 9.8 parts of micron aluminum nitride powder and 0.9 part of nano aluminum nitride powder according to the mass part ratio; the mass ratio of the inorganic compound to the organic solvent is 7: 8; the mass of the dispersing agent is 8% of the total mass of the inorganic compound and the organic solvent; then, adding a bis-diazacyclo cross-linking agent, and stirring at a stirring speed of 1900rpm for 35min to obtain a mixed material 1; wherein, the mass of the cross-linking agent is 0.8 percent of the total mass of the inorganic compound and the organic solvent;
dispersing the mixed binder in deionized water, dispersing for 42min at a dispersion speed of 1550rpm, and stirring for 45min at a stirring speed of 2000rpm to obtain a mixed material 2; wherein the mass ratio of the mixed binder to the deionized water is 1: 19; the mixed binder comprises 4.8 parts of PVDF, 1.8 parts of sodium polyacrylate and 5.7 parts of CMC in parts by mass;
uniformly mixing lithium siloxane, the mixed material 1 and the mixed material 2 according to the mass ratio of 0.4:2.5:7, and stirring at the stirring speed of 2300rpm for 40min to prepare composite coating diaphragm slurry;
and step 3:
firstly, coating the composite coating diaphragm slurry obtained in the step 2 on one side of the polyethylene base film subjected to acidification treatment in the step 1 in a gravure coating mode, wherein the coating speed is 23 m/min; and fully drying at the temperature of 60 ℃ to obtain the composite coating diaphragm with the single-side coating thickness of 2.5 mu m and high conductive performance.
Comparative example 2
Compared with example 2, in the preparation method of the composite coating diaphragm slurry in step 2, no lithium siloxane is added, and the rest steps and parameters are consistent with example 2.
Example 3
A preparation method of a composite coating diaphragm with high conductivity comprises the following steps:
step 1: base film acidification treatment
Coating a nitric acid aqueous solution with the mass concentration of 10% on the surface of the polyethylene base film, carrying out acidification treatment on the polyethylene base film, then cleaning the surface of the polyethylene base film by using deionized water, and drying for later use;
step 2: preparation of composite coating diaphragm slurry
Firstly, adding an inorganic compound and a dispersing agent into an organic solvent propylene glycol, dispersing for 45min at a dispersion speed of 1400rpm, and stirring for 180min at a stirring speed of 2500 rpm; wherein the inorganic compound comprises 6.0 parts of micron alumina powder, 0.5 part of nano alumina powder, 10.0 parts of micron aluminum nitride powder and 1.0 part of nano aluminum nitride powder according to the mass part ratio; the mass ratio of the inorganic compound to the organic solvent is 7.5: 8; the mass of the dispersing agent is 10% of the total mass of the inorganic compound and the organic solvent; then adding a bis-diazacyclo cross-linking agent, and stirring at a stirring speed of 2000rpm for 30min to obtain a mixed material 1; wherein the mass of the cross-linking agent is 1.0 percent of the total mass of the inorganic compound and the organic solvent;
dispersing the mixed binder in deionized water, dispersing for 45min at a dispersion speed of 1600rpm, and stirring for 50min at a stirring speed of 2300rpm to obtain a mixed material 2; wherein the mass ratio of the mixed binder to the deionized water is 1: 20; the mixed binder comprises 5.0 parts of PVDF, 2.0 parts of sodium polyacrylate and 6.0 parts of CMC in parts by mass;
uniformly mixing lithium siloxane, the mixed material 1 and the mixed material 2 according to the mass ratio of 0.5:3.0:7, and stirring for 45min at the stirring speed of 2500rpm to prepare composite coating diaphragm slurry;
and step 3:
firstly, coating the composite coating diaphragm slurry obtained in the step 2 on one side of the polyethylene base film subjected to acidification treatment in the step 1 in a gravure coating mode, wherein the coating speed is 25 m/min; and fully drying at the temperature of 65 ℃ to obtain the composite coating diaphragm with the single-side coating thickness of 3.0 mu m and high conductive performance.
Comparative example 3
Comparative example 3 in comparison to example 3, in the preparation method of the composite coating separator slurry in step 2, PVDF binder was used instead of the mixed binder, and the remaining steps and parameters were kept consistent with example 3.
Comparative example 4
Comparative example 4 in comparison with example 3, in the preparation method of the composite coating separator slurry in step 2, no crosslinking agent was added, and the remaining steps and parameters were kept consistent with example 3.
The ion conductivity tests were performed on the high-conductivity composite-coated separators prepared in examples 1 to 3 and the separators prepared in comparative examples 1 to 3 using the electrochemical workstation of CHI660E of chenhua, and the test data are shown in the following table:
as can be seen from the comparison results of example 1 and comparative example 1, the ionic conductivity of the separator was significantly improved after the polyethylene-based film was acidified. The main reason is that the chemical bond energy on the surface of the organic matter can be improved by the acidification treatment, the activation sites on the surface of the diaphragm are excited, and the attachment of Li ions is increased to prepare for the subsequent electrochemical reaction.
As can be seen from the comparison results of example 2 and comparative example 2, the ion conductivity of the separator produced after adding lithium siloxane to the slurry was significantly increased, and it can be inferred that lithium ions were released from lithium siloxane.
As can be seen from a comparison of example 3 and comparative example 3, the ionic conductivity of the separator prepared using the mixed binder in the slurry was significantly increased compared to that of the separator prepared using the PVDF binder. The main reason is that the molecular chain functional groups in the mixed binder are in interval chain distribution, so that steric hindrance exists, the cross-linking among molecular chains is effectively inhibited, the mobility of the molecular chains is improved, and the ion conduction rate is improved.
As can be seen from the comparison between the example 3 and the comparative example 4, the existence of the cross-linking agent can greatly improve the diffusion uniformity of the electrolyte on the surface of the diaphragm, and the liquid absorption rate and the liquid saturation rate are both greatly improved.
The test method and the test data of the liquid absorption rate and the liquid saturation rate are as follows:
the composite coated separator with high conductivity prepared in examples 1 to 3 and the separator prepared in comparative examples 1 to 3 were each cut to have a length and width of 150mm x 150mm as a separator sample, and the mass m1 before immersion was weighed. And (3) placing the sample in electrolyte, taking out after sealing and soaking for 1h, wiping the electrolyte on the surface of the sample by using a dust-free cloth, and weighing the soaked mass m 2. And spreading the weighed sample flatly, standing for 1h in a room temperature environment, and weighing the mass m3 of the liquid retention diaphragm.
The liquid absorption rate is ((m2-m1))/m1 is 100%, and the liquid retention rate is ((m3-m1))/m1 is 100%. The measurements of the 3 samples were averaged after the test was completed.
Example 4
The composite coating separators with conductive properties prepared in examples 1 to 3 and the separators prepared in comparative examples 1 to 3 were fabricated into lithium batteries. The positive electrode material is a ternary material (NCM523) (purchased from Union solid Li new materials), the negative electrode material is graphite (fibrate-rubicin), the solute of the electrolyte is LiPF6 (the solvent is a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate), and the semi-cell is assembled by EC: DMC ═ 1:1 by mass). The cathode is formed by mixing graphite, a conductive agent (Keqin carbon black) and a binder SBR (styrene butadiene rubber latex) (Shenzhen Yitong) according to a mass ratio of 8:0.8:1.2, and the anode is formed by mixing a cathode material, conductive carbon black (Shenzhen Kezhida) and a binder PVDF (Chengdu Kelong) according to a mass ratio of 8:1: 1.
The lithium battery prepared in the embodiment is subjected to electrochemical performance cycle test by adopting the high-performance battery detection system of Shenzhen Xinwei CT-4008-5V12A, and the test results are shown in the following table:
| lithium battery numbering | 1 | 2 | 3 | 4 | 5 | 6 | 6 |
| Diaphragm | Example 1 | Comparative example 1 | Example 2 | Comparative example 2 | Example 3 | Comparative example 3 | Comparative example 4 |
| Capacity retention ratio (cycle 50 weeks)% | 96.6 | 90.3 | 96.7 | 89.3 | 95.9 | 90.5 | 90.2 |
As can be seen from the above table, the lithium batteries prepared by the composite coating separators with high conductivity prepared in examples 1 to 3 have higher capacity retention rate, improved electrochemical performance and prolonged service life compared with the lithium batteries prepared by the separators prepared in comparative examples 1 to 3.
The composite coated separator with high conductive performance according to the present invention was prepared by adjusting the process parameters according to the present disclosure, and exhibited substantially the same performance as example 1.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of a composite coating diaphragm with high conductivity is characterized by comprising the following steps: the method comprises the following steps:
step 1: base film acidification treatment
Soaking the polyethylene base film in acid liquor for acidification treatment, then cleaning the surface of the polyethylene base film by using deionized water, and drying for later use;
step 2: preparation of composite coating diaphragm slurry
Adding an inorganic compound and a dispersant into an organic solvent for uniform dispersion, adding a bis-diazacyclo cross-linking agent, and uniformly mixing to obtain a mixed material 1; the inorganic compound comprises micron alumina powder, nanometer alumina powder, micron aluminum nitride powder and nanometer aluminum nitride powder;
dispersing the mixed binder in deionized water to obtain a mixed material 2; the mixed binder is a mixture of PVDF, sodium polyacrylate and CMC;
uniformly mixing lithium siloxane, the mixed material 1 and the mixed material 2 to prepare composite coating diaphragm slurry;
and step 3: film production
And (3) coating the composite coating diaphragm slurry obtained in the step (2) on one side or two sides of the polyethylene base film subjected to acidification treatment in the step (1), and drying to obtain the composite coating diaphragm with high conductivity.
2. The method of claim 1, wherein: in the step 1, the acid solution is a hydrochloric acid aqueous solution, a nitric acid aqueous solution or a sulfuric acid aqueous solution with the concentration of 1% -20%.
3. The method of claim 1, wherein: in the step 2, the mass part ratio of the micron alumina powder, the nanometer alumina powder, the micron aluminum nitride powder and the nanometer aluminum nitride powder is (5.5-6.0): (0.3-0.5): (9.5-10.0): (0.8-1.0).
4. The method of claim 3, wherein: the dispersing agent comprises one or a mixture of polyethylene glycol, polyvinyl alcohol and polyvinylpyrrolidone in any proportion;
the organic solvent comprises one or a mixture of isopropanol, n-propanol and propylene glycol in any proportion.
5. The method of claim 4, wherein: the mass part ratio of the inorganic compound to the organic solvent is (6-7.5): 8;
the mass of the dispersant is 5-10% of the total mass of the inorganic compound and the organic solvent;
the mass of the bis-diazacyclo cross-linking agent is 0.5-1.0% of the total mass of the inorganic compound and the organic solvent.
6. The method of claim 1, wherein: in the mixed binder, the mass part ratio of PVDF, sodium polyacrylate and CMC is (4.5-5): (1.5-2): (5.5-6);
the proportion of the total mass of the PVDF, the sodium polyacrylate and the CMC to the mass of the deionized water is 1: (18-20).
7. The method of claim 1, wherein: the mass part ratio of the lithium siloxane to the mixed materials 1 and 2 is (0.3-0.5): (2-3): 7.
8. the method of claim 1, wherein: in the step 3, the coating mode is gravure coating, and the coating speed is 20-25 m/min;
the drying temperature is 55-70 ℃;
the coating thickness is 2.0-3.0 μm.
9. A composite coating diaphragm with high conductive performance, which is prepared by the preparation method of any one of claims 1 to 8.
10. A lithium battery comprising a positive electrode, a negative electrode, an electrolyte and the high-conductivity composite-coated separator according to claim 9.
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