CN117577934A - Electrolyte film and preparation method thereof - Google Patents
Electrolyte film and preparation method thereof Download PDFInfo
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- CN117577934A CN117577934A CN202410018314.8A CN202410018314A CN117577934A CN 117577934 A CN117577934 A CN 117577934A CN 202410018314 A CN202410018314 A CN 202410018314A CN 117577934 A CN117577934 A CN 117577934A
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- acetonitrile
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 76
- 238000002360 preparation method Methods 0.000 title abstract description 19
- 239000005518 polymer electrolyte Substances 0.000 claims abstract description 55
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims abstract description 50
- 239000002243 precursor Substances 0.000 claims abstract description 37
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 29
- 239000011231 conductive filler Substances 0.000 claims abstract description 27
- 239000005543 nano-size silicon particle Substances 0.000 claims abstract description 27
- 229920001610 polycaprolactone Polymers 0.000 claims abstract description 21
- 239000004632 polycaprolactone Substances 0.000 claims abstract description 20
- 239000011248 coating agent Substances 0.000 claims abstract description 19
- 238000000576 coating method Methods 0.000 claims abstract description 19
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 claims abstract description 16
- 238000007493 shaping process Methods 0.000 claims abstract description 16
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 99
- 239000010408 film Substances 0.000 claims description 39
- 238000003756 stirring Methods 0.000 claims description 21
- 239000007788 liquid Substances 0.000 claims description 17
- 238000001035 drying Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 12
- 239000011812 mixed powder Substances 0.000 claims description 11
- -1 lithium aluminum chromium phosphate Chemical compound 0.000 claims description 10
- 239000012528 membrane Substances 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 3
- NRJJZXGPUXHHTC-UHFFFAOYSA-N [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] Chemical compound [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] NRJJZXGPUXHHTC-UHFFFAOYSA-N 0.000 claims description 3
- RJEIKIOYHOOKDL-UHFFFAOYSA-N [Li].[La] Chemical compound [Li].[La] RJEIKIOYHOOKDL-UHFFFAOYSA-N 0.000 claims description 3
- CVJYOKLQNGVTIS-UHFFFAOYSA-K aluminum;lithium;titanium(4+);phosphate Chemical compound [Li+].[Al+3].[Ti+4].[O-]P([O-])([O-])=O CVJYOKLQNGVTIS-UHFFFAOYSA-K 0.000 claims description 3
- 150000003949 imides Chemical class 0.000 claims description 3
- 239000010409 thin film Substances 0.000 claims description 2
- 238000007606 doctor blade method Methods 0.000 claims 1
- 210000001787 dendrite Anatomy 0.000 abstract description 19
- 150000002500 ions Chemical class 0.000 abstract description 14
- 239000011159 matrix material Substances 0.000 abstract description 7
- 230000035515 penetration Effects 0.000 abstract description 6
- 238000013329 compounding Methods 0.000 abstract description 5
- 229920000642 polymer Polymers 0.000 abstract description 5
- 238000004873 anchoring Methods 0.000 abstract description 3
- 239000007787 solid Substances 0.000 abstract description 3
- 230000001934 delay Effects 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 17
- 239000000463 material Substances 0.000 description 16
- 238000012360 testing method Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
- 239000002904 solvent Substances 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 7
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 7
- 239000004810 polytetrafluoroethylene Substances 0.000 description 7
- 238000005054 agglomeration Methods 0.000 description 6
- 230000002776 aggregation Effects 0.000 description 6
- 238000001291 vacuum drying Methods 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 239000007784 solid electrolyte Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910006270 Li—Li Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910003002 lithium salt Inorganic materials 0.000 description 3
- 159000000002 lithium salts Chemical class 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- IAHFWCOBPZCAEA-UHFFFAOYSA-N succinonitrile Chemical compound N#CCCC#N IAHFWCOBPZCAEA-UHFFFAOYSA-N 0.000 description 3
- 235000012431 wafers Nutrition 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000003365 glass fiber Substances 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000011241 protective layer Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000005279 LLTO - Lithium Lanthanum Titanium Oxide Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 125000004386 diacrylate group Chemical group 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 239000011256 inorganic filler Substances 0.000 description 1
- 229910003475 inorganic filler Inorganic materials 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000007582 slurry-cast process Methods 0.000 description 1
- 239000010936 titanium Substances 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
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
-
- 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)
- Engineering & Computer Science (AREA)
- Electrochemistry (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
Abstract
The invention belongs to the technical field of solid polymer electrolytes, and particularly relates to an electrolyte film and a preparation method thereof. The preparation method comprises the steps of preparing a first polymer electrolyte by adopting an inorganic conductive filler, lithium bis (trifluoromethanesulfonyl) imide, polyethylene oxide and polycaprolactone; and then coating a second polymer electrolyte precursor solution prepared from nano silicon, lithium bis (trifluoromethanesulfonyl) imide and polyethylene oxide on the first polymer electrolyte, and shaping to obtain the electrolyte film. The preparation method adopts the nano silicon and PEO-based electrolyte to prepare the negative electrode side modified layer in a compounding way, is used for anchoring the lithium dendrite at the negative electrode side, and effectively delays the penetration of the lithium dendrite to the electrolyte under high current density; adopts chain segment polymer PEO and PCL as a matrix, and inorganic conductive filler and electrolyte are compounded to prepare a positive electrode side modified layer, so that the ion conductivity is improved.
Description
Technical Field
The invention belongs to the technical field of solid polymer electrolytes, and particularly relates to an electrolyte film and a preparation method thereof.
Background
The lithium ion battery is widely applied to energy storage and 3C digital products because of the advantages of high energy density, no memory effect, environmental friendliness and the like. However, with the continuous expansion of new energy automobile markets in recent years, the limited energy density of the traditional liquid lithium ion battery is gradually unable to meet the actual demands of the increasingly expanded energy markets.
The PEO (polyethylene oxide) based solid electrolyte is modified by adopting solid electrolyte particles as inorganic active filler, and the complex solid electrolyte which takes polymer PEO as a matrix and is doped with lithium salt is prepared by complexing lithium salt with better interface stability with PEO, so that the ionic conductivity and the cycling stability can be effectively improved. Based on the above, the Chinese patent publication No. CN108963327A discloses an inorganic filler composite PEO solid electrolyte material, which consists of PEO, inorganic powder with high ion conductivity and lithium salt, improves the ion conductivity and mechanical property at room temperature, but the physical barrier provided by a protective layer can not completely inhibit the puncture of lithium dendrites under high current density.
The Chinese patent publication No. CN111463480A discloses a method for preparing a filter membrane-based high-performance composite solid electrolyte film, wherein the film comprises a filter membrane polymer electrolyte matrix and garnet Li 6.5 La 3 Zr 1.5 Ta 0.5 O 1 The solid inorganic electrolyte layer is composed, the conductivity is high at room temperature, the electrochemical property is stable, but the film has a rigid surface which is unfavorable for the tight contact of interfaces, and meanwhile, the safety in the practical application of the battery can be influenced by the fragile characteristic of the inorganic layer, and the film is expensive and unfavorable for mass production.
The Chinese patent with publication number of CN113299985A proposes a preparation method of succinonitrile double-layer composite polymer electrolyte, which comprises the steps of dissolving succinonitrile and lithium bis (trifluoromethanesulfonyl) imide in a polyethylene glycol diacrylate solvent, and adding a photoinitiator to prepare a mixed solvent; and (3) preparing a PEO polymer electrolyte membrane by adopting a slurry casting drying method, adhering the dried PEO polymer electrolyte membrane to glass fibers, adding excessive mixed solvent to completely soak the glass fibers, and finally pressing and ultraviolet curing by using a transparent glass plate to obtain the succinonitrile-based double-layer composite polymer electrolyte. The electrolyte has good contact property with the electrode near the modified layer of the cathode and wide electrochemical window, but has limited inhibition effect on lithium dendrite under high current density, and has stable interface and inorganic contribution.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: an electrolyte film and a method for manufacturing the same are provided, which can improve electron conductivity while suppressing penetration of lithium dendrites at a high current density.
In order to solve the technical problems, the invention adopts the following technical scheme: a method for preparing an electrolyte film, comprising the steps of:
s1: adding inorganic conductive filler and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) into acetonitrile, stirring, adding mixed powder of polyethylene oxide (PEO) and Polycaprolactone (PCL), and continuously stirring to obtain a first polymer electrolyte precursor solution;
s2: coating and shaping the first polymer electrolyte precursor liquid to obtain a first polymer electrolyte;
s3: pouring nano silicon and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile for stirring, adding polyethylene oxide, and continuously stirring to obtain a second polymer electrolyte precursor solution;
s4: and coating the second polymer electrolyte precursor solution on the first polymer electrolyte, and shaping to obtain the electrolyte film.
The invention adopts another technical scheme that: an electrolyte film prepared by the preparation method of the electrolyte film.
The invention has the beneficial effects that: the invention provides a preparation method of an asymmetric double-layer electrolyte film, wherein a modified layer is prepared on the negative electrode side by compounding nano silicon and PEO-based electrolyte, and is used for anchoring lithium dendrites on the negative electrode side, so that the penetration of the lithium dendrites on the electrolyte under high current density is effectively delayed; the positive electrode side adopts chain segment polymer PEO and PCL as matrixes, and simultaneously adopts inorganic conductive filler and electrolyte for compounding, so that the ionic conductivity is further improved.
Drawings
Fig. 1 shows the results of the ion conductivity test of the first embodiment of the present invention and the first comparative example, wherein the abscissa is: the real part of the impedance, ordinate is: an impedance imaginary part;
FIG. 2 shows the constant current charge and discharge test results of the Li-Li symmetrical battery of comparative example I of the present invention;
fig. 3 shows the constant current charge and discharge test results of the Li-Li symmetric battery of comparative example one of the present invention.
Detailed Description
In order to describe the technical contents, the achieved objects and effects of the present invention in detail, the following description will be made with reference to the embodiments in conjunction with the accompanying drawings.
A method for preparing an electrolyte film, comprising the steps of:
s1: adding inorganic conductive filler and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile, stirring, adding mixed powder of polyethylene oxide and polycaprolactone, and continuously stirring to obtain a first polymer electrolyte precursor solution;
s2: coating and shaping the first polymer electrolyte precursor liquid to obtain a first polymer electrolyte;
s3: pouring nano silicon and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile for stirring, adding polyethylene oxide, and continuously stirring to obtain a second polymer electrolyte precursor solution;
s4: and coating the second polymer electrolyte precursor solution on the first polymer electrolyte, and shaping to obtain the electrolyte film.
From the above description, the beneficial effects of the invention are as follows: the preparation method of the invention firstly prepares the positive electrode side of the electrolyte film, adopts the segmented polymer PEO and PCL as the matrix, has good compatibility between PCL and PEO, can further reduce the crystallinity of PEO and improve the ionic conductivity; meanwhile, inorganic conductive filler and electrolyte are compounded, and the inorganic conductive filler forms a continuous ion conductive network in the electrolyte matrix, so that the transmission efficiency of lithium ions is improved.
Then preparing an electrolyte filmThe negative electrode side is prepared by compounding nano silicon and PEO-based electrolyte, wherein nano silicon particles can reduce the crystallinity of the polymer electrolyte, improve the ionic conductivity and effectively delay the penetration of lithium dendrites to the electrolyte under high current density. Specifically, the lithium dendrite on the negative electrode side first pierces the electrolyte near the negative electrode side during charging. The negative side is rich in nano silicon, and when the lithium dendrite contacts the layer, the nano silicon and locally deposited lithium undergo alloying reaction to produce Li x Si compound, delay the further penetration of lithium dendrite; the nano silicon is used as a cathode material with extremely high expansion rate, and huge volume expansion is generated after lithiation, so that the expansion effectively improves the mechanical strength of the protective layer and the overall lithium dendrite resistance of the electrolyte.
The double-layer asymmetric structure obtained by the preparation method has the advantages that only one layer of nano silicon exists, so that the conditions of main ion conductive material proportion reduction and ion conductivity reduction caused by filling of a large amount of nano silicon can be prevented; and severe agglomeration caused by the combination of a large amount of nano silicon and inorganic conductive filler can be avoided, and the agglomeration can obstruct an ion transmission path.
Further, the weight ratio of the polyethylene oxide, the polycaprolactone, the lithium bistrifluoromethane sulfonyl imide and the inorganic conductive filler in the S1 is 1.63-1.98: 1.63 to 1.98:1.7 to 2.3:1.
from the above description, the higher the PEO ratio, the better the electrolyte mechanical properties, but with reduced ionic conductivity and mobility; in a certain range, the higher the proportion of the inorganic conductive filler is, the faster the transmission efficiency of lithium ions is, but the too high proportion of the filler is easy to cause agglomeration of particles, and the electric performance is reduced; PCL can reduce the crystallinity of PEO, forming more lithium ion migration sites within the bulk phase; therefore, in order to balance the electrical properties and the mechanical properties of the electrolyte, the weight ratio of polyethylene oxide, polycaprolactone, lithium bistrifluoromethane sulfonyl imide and inorganic conductive filler in S1 is defined to be 1.63-1.98: 1.63 to 1.98:1.7 to 2.3:1.
further, the weight ratio of acetonitrile to mixed powder in S1 is 11-13: 1.
from the above description, too high acetonitrile ratio can result in too high fluidity of the precursor and poor coating effect; too low a proportion of acetonitrile causes agglomeration of PEO and PCL, thus defining a weight ratio of acetonitrile to mixed powder of 11 to 13:1.
further, the inorganic conductive filler includes at least one of Lithium Lanthanum Zirconium Oxide (LLZO), lithium Aluminum Titanium Phosphate (LATP), lanthanum Lithium Titanate (LLTO), lithium aluminum chromium phosphate (LAGP).
Further, S1 is specifically: adding inorganic conductive filler and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile, stirring for 5-10 min at the speed of 800-1200 r/min, adding mixed powder of polyethylene oxide and polycaprolactone, and continuously stirring for 20-24 h at the speed of 800-1200 r/min to obtain a first polymer electrolyte precursor solution.
From the above description, too low a rotational speed during magnetic stirring can cause uneven components of the precursor liquid, and too high a rotational speed can introduce too many bubbles to affect the material performance.
Further, the shaping in S1 and S2 comprises standing and drying sequentially, wherein the drying temperature is 60-65 ℃ and the drying time is 15-20 h.
From the above description, it is clear that too low a temperature at the time of drying may cause incomplete evaporation of acetonitrile, remain in the electrolyte, and too high a drying temperature may affect the material properties, thus limiting the drying temperature to 60 to 65 ℃. Too short a drying time may result in solvent residues, too long a time may result in LiTFSI absorbing water, increasing the water content of the electrolyte, thus limiting the drying time to 15-20 hours.
Further, the standing time is 10-20 min.
From the above description, it is known that the mixture is left to stand until preliminary setting.
Further, the bubbles in the first polymer electrolyte precursor solution or the second polymer electrolyte precursor solution need to be removed before the S1 and S2 are coated.
From the above description, bubbles may cause uneven coating of materials and unstable performance.
Further, the weight ratio of the polyethylene oxide, the lithium bistrifluoro methanesulfonimide and the nano silicon in the S3 is 3.48-3.82: 1.84 to 2.1:1.
from the above description, the greater the PEO ratio, the better the mechanical properties of the electrolyte, but with reduced ionic conductivity and mobility; the increase of the proportion of nano silicon can improve the lithium dendrite resistance of the electrolyte, but the too high proportion of nano silicon easily leads to agglomeration of particles and reduces the electrical performance.
Further, the weight ratio of acetonitrile to polyethylene oxide in S3 is 11-13: 1.
further, the coating in S2 and S4 is blade coating, the blade gap of S2: doctor gap of S4 = 3:2 to 1.
From the above description, it is understood that the doctor blade gap affects the electrolyte thickness, and the present invention controls the thickness ratio of the double layer electrolyte by controlling the doctor blade gap, and the larger the thickness ratio of the second polymer electrolyte is, the lower the overall electrolyte conductivity is.
The invention adopts another technical scheme that: an electrolyte film prepared by the preparation method of the electrolyte film.
From the above description, it is apparent that the electrolyte thin film of the present invention has an asymmetric double-layer structure, which can improve both the resistance to lithium dendrites and the lithium ion transport efficiency.
The first embodiment of the invention is as follows: a preparation method of an electrolyte film comprises the following steps:
s1: adding 4392g of acetonitrile into a container, adding 100g of inorganic conductive filler and 200g of lithium bistrifluoromethane sulfonyl imide into acetonitrile, magnetically stirring at a rotating speed of 1000r/min for 5min, adding 183g of mixed powder of polyethylene oxide and 183g of polycaprolactone, and magnetically stirring for 24h at a rotating speed of 1000r/min to obtain a first polymer electrolyte precursor liquid; the inorganic conductive filler is lithium lanthanum zirconium oxide.
S2: placing the first polymer electrolyte in a bubble removing barrel, vacuum extracting bubbles, pouring the bubbles on a smooth and clean polytetrafluoroethylene plate, uniformly coating precursor liquid on the polytetrafluoroethylene plate by adopting a scraper with a gap of 1500um, standing the coated material in a room temperature environment for 20min for preliminary shaping, and then placing the material in a vacuum oven at 60 ℃ for vacuum drying for 20h until solvent acetonitrile is completely evaporated, thus obtaining the first polymer electrolyte.
S3: 100g of nano silicon and 200g of lithium bis (trifluoromethanesulfonyl) imide are poured into 4320g of acetonitrile to be magnetically stirred for 5min at the rotating speed of 1000r/min, 360g of polyethylene oxide is added to be magnetically stirred for 24h at the rotating speed of 1000r/min, and a second polymer electrolyte precursor liquid is obtained.
S4: and (3) placing the second polymer electrolyte precursor solution in a bubble removal barrel, vacuum extracting bubbles, uniformly coating the precursor solution on the dried first polymer electrolyte by adopting a scraper with a gap of 1000um, standing the coated material in a room temperature environment for 20min for preliminary shaping, and then placing the material in a vacuum oven at 60 ℃ for vacuum drying for 20h until solvent acetonitrile is completely evaporated, thus obtaining the electrolyte film.
The second embodiment of the invention is as follows: the electrolyte membrane prepared by the preparation method of the first embodiment is adopted.
The first comparative example of the present invention is: the preparation method of the conventional electrolyte film comprises the following steps:
s1: 864g of acetonitrile is weighed and injected into a container, 20g of conductive particles and 39g of lithium bistrifluoromethane sulfonyl imide are added into acetonitrile and magnetically stirred for 5min at a rotating speed of 1000r/min, 72g of polyethylene oxide is weighed and added into the stirred container, and after the polyethylene oxide is completely added, the mixture is magnetically stirred for 24h at room temperature, so as to obtain a polymer electrolyte precursor liquid.
S2: and (3) placing the polymer electrolyte precursor liquid into a bubble removing machine, vacuumizing to remove bubbles mixed in stirring, taking out, uniformly coating the precursor liquid on a polytetrafluoroethylene plate by adopting a scraper with a gap of 2000um, standing for 20min in a room temperature environment, primarily shaping, and then placing into a vacuum oven for drying at 60 ℃ for 24h to obtain the composite electrolyte film.
Examples one and comparative example one test: ion conductivity test
The testing method comprises the following steps: the electrolyte film prepared in the first embodiment and the first comparative embodiment is cut into a wafer with the diameter of 16mm, two stainless steel wafers with the diameter of 14mm and the thickness of 0.5mm are taken as double-blocking electrodes, and the button cell assembled with the structure of stainless steel sheet-electrolyte film-stainless steel sheet is subjected to ion conductivity test at 45 ℃ in the frequency range: 1 Hz-4 MHz. The test results are shown in Table 1 and FIG. 1 (abscissa: real part of impedance, ordinate: imaginary part of impedance).
TABLE 1
As can be seen from fig. 1 and table 1, the electrolyte film prepared in example one has a higher ionic conductivity than that of comparative example one, which demonstrates that the electrolyte film of the present invention can improve ionic conductivity through component optimization.
Examples one and comparative example one test: constant-current charge and discharge test for Li-Li symmetrical battery
The testing method comprises the following steps: the electrolyte film prepared in the first embodiment and the electrolyte film prepared in the first comparative embodiment are cut into wafers with the diameter of 16mm, a lithium sheet with the diameter of 14mm is used as an electrode in a glove box, a symmetrical battery of the lithium sheet, the electrolyte film and the lithium sheet is assembled, and after packaging, constant current charge and discharge tests are carried out at 60 ℃, wherein each cycle comprises constant current charge with the primary current of 0.4mA for 30min and constant current discharge with the primary current of 0.4mA for 30 min. The test results are shown in fig. 2 and 3, and fig. 2 and 3 show that the assembled symmetrical battery of the first example has no short circuit during 100h cycle, and the battery of the first comparative example has obvious short circuits at 50h and 65h, indicating that the optimized first example has better lithium dendrite resistance.
The third embodiment of the invention is as follows: a preparation method of an electrolyte film comprises the following steps:
s1: placing 3586g of acetonitrile in a container, adding 100g of inorganic conductive filler and 170g of lithium bistrifluoromethane sulfonyl imide into the acetonitrile, magnetically stirring at a rotating speed of 800r/min for 10min, adding 163g of mixed powder of polyethylene oxide and 163g of polycaprolactone, and magnetically stirring for 22h at a rotating speed of 800r/min to obtain a first polymer electrolyte precursor liquid; the inorganic conductive filler is lithium aluminum chromium phosphate (Li) 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 )。
S2: placing the first polymer electrolyte in a bubble removing barrel, vacuum extracting bubbles, pouring the bubbles on a smooth and clean polytetrafluoroethylene plate, uniformly coating precursor liquid on the polytetrafluoroethylene plate by adopting a scraper with a gap of 1500um, standing the coated material in a room temperature environment for 10min for preliminary shaping, and then placing the material in a vacuum oven at 65 ℃ for vacuum drying for 15h until solvent acetonitrile is completely evaporated, thus obtaining the first polymer electrolyte.
S3: 100g of nano silicon and 210g of lithium bistrifluoromethylsulfonyl imide are poured into 4202g of acetonitrile and magnetically stirred for 10min at the speed of 800r/min, 382g of polyethylene oxide is added and magnetically stirred for 22h at the speed of 800r/min, and a second polymer electrolyte precursor liquid is obtained.
S4: and (3) after placing the second polymer electrolyte precursor solution in a bubble removal barrel for vacuum extraction of bubbles, uniformly coating the precursor solution on the dried first polymer electrolyte by adopting a scraper with a gap of 750um, standing the coated material in a room temperature environment for 10min for preliminary shaping, and then placing the material in a vacuum oven at 65 ℃ for vacuum drying for 15h until solvent acetonitrile is completely evaporated, thus obtaining the electrolyte film.
The fourth embodiment of the invention is as follows: the inorganic conductive filler is. A preparation method of an electrolyte film comprises the following steps:
s1: 5148g of acetonitrile is placed in a container, then 100g of inorganic conductive filler and 230g of lithium bis (trifluoromethanesulfonyl) imide are added into the acetonitrile and magnetically stirred for 6min at the rotating speed of 1200r/min, and then 198g of mixed powder of polyethylene oxide and 198g of polycaprolactone is added and magnetically stirred for 20h at the rotating speed of 1200r/min, so that a first polymer electrolyte precursor liquid is obtained; the inorganic conductive filler is lithium aluminum titanium phosphate (Li) 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 ) And lanthanum lithium titanate (La) 0.56 Li 0.33 TiO 3 )。
S2: placing the first polymer electrolyte in a bubble removing barrel, vacuum extracting bubbles, pouring the bubbles on a smooth and clean polytetrafluoroethylene plate, uniformly coating precursor liquid on the polytetrafluoroethylene plate by adopting a scraper with a gap of 1500um, standing the coated material in a room temperature environment for 15min for preliminary shaping, and then placing the material in a vacuum oven at 63 ℃ for vacuum drying for 18h until solvent acetonitrile is completely evaporated, thus obtaining the first polymer electrolyte.
S3: 100g of nano silicon and 184g of lithium bistrifluoromethylsulfonyl imide are poured into 4524g of acetonitrile and magnetically stirred for 6min at the rotation speed of 1200r/min, 348g of polyethylene oxide is added and magnetically stirred for 20h at the rotation speed of 1200r/min, and the second polymer electrolyte precursor liquid is obtained.
S4: and (3) placing the second polymer electrolyte precursor solution in a bubble removal barrel, vacuum extracting bubbles, uniformly coating the precursor solution on the dried first polymer electrolyte by adopting a scraper with a gap of 500um, standing the coated material in a room temperature environment for 15min for preliminary shaping, and then placing the material in a vacuum oven at 63 ℃ for vacuum drying for 18h until solvent acetonitrile is completely evaporated, thus obtaining the electrolyte film.
In summary, the preparation method of the electrolyte film provided by the invention has the following advantages:
1. the electrolyte film prepared by the preparation method provided by the invention adopts a double-layer asymmetric structure, and realizes the improvement of energy density while matching with a metal lithium negative electrode. The nano silicon is only in one layer, so that the condition that the ion conductivity is reduced due to filling of a large amount of nano silicon can be prevented; and the agglomeration blocking of the ion transmission path after the combination of a large amount of nano silicon and inorganic conductive filler can be avoided.
2. The negative electrode side modified layer is prepared by compounding nano silicon and PEO-based electrolyte and is used for anchoring lithium dendrites on the negative electrode side. The nano silicon particles in the modified layer can reduce the crystallinity of the polymer electrolyte, improve the ionic conductivity, react with lithium to limit the growth of lithium dendrites, and simultaneously bring about volume expansion in the process of reacting with lithium, so that a certain mechanical strength is provided for the modified layer, the integral lithium dendrite resistance of the electrolyte is improved in an auxiliary manner, and the penetration of lithium dendrites to the electrolyte under high current density is effectively delayed.
3. The nano silicon is adopted for modification, so that the silicon reserves are large, and the cost is low.
4. The segmented polymer PEO and PCL are used as the matrix to prepare the positive electrode side, the PCL and PEO have good compatibility, the crystallinity of PEO can be further reduced, and the ion conductivity is improved; meanwhile, inorganic conductive filler and electrolyte are compounded, and the inorganic conductive filler forms a continuous ion conductive network in the electrolyte matrix, so that the transmission efficiency of lithium ions is improved.
5. In order to prevent LiTFSI from absorbing water due to overlong time during drying, the water content of the electrolyte is increased, and the drying time is limited to 15-20 h.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent changes made by the specification and drawings of the present invention, or direct or indirect application in the relevant art, are included in the scope of the present invention.
Claims (10)
1. A method for producing an electrolyte film, comprising the steps of:
s1: adding inorganic conductive filler and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile, stirring, adding mixed powder of polyethylene oxide and polycaprolactone, and continuously stirring to obtain a first polymer electrolyte precursor solution;
s2: coating and shaping the first polymer electrolyte precursor liquid to obtain a first polymer electrolyte;
s3: pouring nano silicon and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile for stirring, adding polyethylene oxide, and continuously stirring to obtain a second polymer electrolyte precursor solution;
s4: and coating the second polymer electrolyte precursor solution on the first polymer electrolyte, and shaping to obtain the electrolyte film.
2. The method for preparing an electrolyte film according to claim 1, wherein the weight ratio of polyethylene oxide, polycaprolactone, lithium bistrifluoromethane sulfonyl imide and inorganic conductive filler in S1 is 1.63-1.98: 1.63 to 1.98:1.7 to 2.3:1.
3. the method for preparing an electrolyte membrane according to claim 1, wherein the weight ratio of acetonitrile to mixed powder in S1 is 11-13: 1.
4. the method for producing an electrolyte thin film according to claim 1, wherein the inorganic conductive filler comprises at least one of lithium lanthanum zirconium oxide, lithium aluminum titanium phosphate, lanthanum lithium titanate, lithium aluminum chromium phosphate.
5. The method for preparing an electrolyte film according to claim 1, wherein S1 specifically comprises: adding inorganic conductive filler and lithium bis (trifluoromethanesulfonyl) imide into acetonitrile, stirring for 5-10 min at the speed of 800-1200 r/min, adding mixed powder of polyethylene oxide and polycaprolactone, and continuously stirring for 20-24 h at the speed of 800-1200 r/min to obtain a first polymer electrolyte precursor solution.
6. The method for producing an electrolyte membrane according to claim 1, wherein the shaping in S1 and S2 includes sequentially performing standing and drying at a temperature of 60 to 65 ℃ for 15 to 20 hours.
7. The method for preparing an electrolyte film according to claim 1, wherein the weight ratio of polyethylene oxide, lithium bistrifluoromethylsulfonyl imide and nano-silicon in the step S3 is 3.48-3.82: 1.84 to 2.1:1.
8. the method for preparing an electrolyte film according to claim 1, wherein the weight ratio of acetonitrile to polyethylene oxide in S3 is 11-13: 1.
9. the method of claim 1, wherein the coating in S2 and S4 is doctor blade coating, and the doctor blade gap of S2: doctor gap of S4 = 3:2 to 1.
10. An electrolyte membrane prepared by the method for preparing an electrolyte membrane according to any one of claims 1 to 9.
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