CN117878530A - Composite diaphragm and preparation method and application thereof - Google Patents
Composite diaphragm and preparation method and application thereof Download PDFInfo
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- CN117878530A CN117878530A CN202311637377.3A CN202311637377A CN117878530A CN 117878530 A CN117878530 A CN 117878530A CN 202311637377 A CN202311637377 A CN 202311637377A CN 117878530 A CN117878530 A CN 117878530A
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- 239000002131 composite material Substances 0.000 title claims abstract description 75
- 238000002360 preparation method Methods 0.000 title claims abstract description 32
- 229920000767 polyaniline Polymers 0.000 claims abstract description 48
- 239000002346 layers by function Substances 0.000 claims abstract description 35
- 239000010410 layer Substances 0.000 claims abstract description 32
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 25
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 21
- 239000001913 cellulose Substances 0.000 claims abstract description 19
- 229920002678 cellulose Polymers 0.000 claims abstract description 19
- 239000002002 slurry Substances 0.000 claims description 34
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 30
- 229910052783 alkali metal Inorganic materials 0.000 claims description 19
- 150000001340 alkali metals Chemical class 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 18
- 239000006185 dispersion Substances 0.000 claims description 15
- 239000002253 acid Substances 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 13
- 239000002585 base Substances 0.000 claims description 11
- 238000001914 filtration Methods 0.000 claims description 10
- 239000007788 liquid Substances 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 239000003999 initiator Substances 0.000 claims description 8
- 239000012065 filter cake Substances 0.000 claims description 5
- 238000001308 synthesis method Methods 0.000 claims description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 239000011734 sodium Substances 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 36
- 230000000052 comparative effect Effects 0.000 description 25
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- 239000000203 mixture Substances 0.000 description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 12
- 229910001416 lithium ion Inorganic materials 0.000 description 12
- 238000001035 drying Methods 0.000 description 10
- 239000000758 substrate Substances 0.000 description 10
- 238000012360 testing method Methods 0.000 description 8
- 150000002500 ions Chemical class 0.000 description 7
- 238000002156 mixing Methods 0.000 description 7
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 229920000098 polyolefin Polymers 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- SCPWMSBAGXEGPW-UHFFFAOYSA-N dodecyl(trimethoxy)silane Chemical compound CCCCCCCCCCCC[Si](OC)(OC)OC SCPWMSBAGXEGPW-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000009472 formulation Methods 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 239000002033 PVDF binder Substances 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
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- 238000000967 suction filtration Methods 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- AZQWKYJCGOJGHM-UHFFFAOYSA-N 1,4-benzoquinone Chemical compound O=C1C=CC(=O)C=C1 AZQWKYJCGOJGHM-UHFFFAOYSA-N 0.000 description 3
- HPTYUNKZVDYXLP-UHFFFAOYSA-N aluminum;trihydroxy(trihydroxysilyloxy)silane;hydrate Chemical class O.[Al].[Al].O[Si](O)(O)O[Si](O)(O)O HPTYUNKZVDYXLP-UHFFFAOYSA-N 0.000 description 3
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 229910052621 halloysite Inorganic materials 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000003574 free electron Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002071 nanotube Substances 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 239000012265 solid product Substances 0.000 description 2
- 239000011550 stock solution Substances 0.000 description 2
- 238000004381 surface treatment Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- GEYOCULIXLDCMW-UHFFFAOYSA-N 1,2-phenylenediamine Chemical compound NC1=CC=CC=C1N GEYOCULIXLDCMW-UHFFFAOYSA-N 0.000 description 1
- WXHLLJAMBQLULT-UHFFFAOYSA-N 2-[[6-[4-(2-hydroxyethyl)piperazin-1-yl]-2-methylpyrimidin-4-yl]amino]-n-(2-methyl-6-sulfanylphenyl)-1,3-thiazole-5-carboxamide;hydrate Chemical compound O.C=1C(N2CCN(CCO)CC2)=NC(C)=NC=1NC(S1)=NC=C1C(=O)NC1=C(C)C=CC=C1S WXHLLJAMBQLULT-UHFFFAOYSA-N 0.000 description 1
- 229910018512 Al—OH Inorganic materials 0.000 description 1
- 102000004310 Ion Channels Human genes 0.000 description 1
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 description 1
- 229910002656 O–Si–O Inorganic materials 0.000 description 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 229920001887 crystalline plastic Polymers 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- RAABOESOVLLHRU-UHFFFAOYSA-N diazene Chemical compound N=N RAABOESOVLLHRU-UHFFFAOYSA-N 0.000 description 1
- 229910000071 diazene Inorganic materials 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- 229910001649 dickite Inorganic materials 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000012456 homogeneous solution Substances 0.000 description 1
- -1 hydrogen ions Chemical class 0.000 description 1
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000010954 inorganic particle Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 229910052622 kaolinite Inorganic materials 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 125000004151 quinonyl group Chemical group 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000002468 redox effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
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- 238000003828 vacuum filtration Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- 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
Landscapes
- Secondary Cells (AREA)
Abstract
The invention discloses a composite diaphragm and a preparation method and application thereof, and belongs to the technical field of new energy. The composite diaphragm provided by the invention comprises a basal layer and a functional layer which are overlapped; the material of the basal layer comprises cellulose; the components of the functional layer include PANI modified HNTs and PEO. The composite diaphragm provided by the invention not only can improve the safety performance of the lithium secondary battery, but also can improve the capacity, the cycle performance and the high-rate working performance of the lithium secondary battery. The invention also provides a preparation method and application of the composite diaphragm.
Description
Technical Field
The invention relates to the technical field of new energy, in particular to a composite diaphragm and a preparation method and application thereof.
Background
The separator is an important component in the battery to prevent short circuits, and also provides a path for smooth movement of lithium ions. With the continuous progress of technology, the demand for safer and more environment-friendly lithium ion batteries is increasing.
Currently, the main current separators used in lithium ion batteries are all made of polyolefin materials, however, the polymers shrink at high temperature and are easy to generate heat accumulation or even cause explosion under the condition of short circuit or local overheating. Therefore, modification of the polyolefin separator is important to improve the safety of the battery.
The commercial polyolefin separator is mainly modified by coating polymethyl methacrylate/alumina, polyvinylidene fluoride/alumina or the like on the surface of polyolefin to improve the heat resistance and safety of the separator through inorganic particles.
However, the above-mentioned coating layer may reduce the ionic conductivity of the separator to some extent, so that the separator exhibits poor performance in high-rate charge and discharge, and the improvement of safety thereof is also unsatisfactory.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a composite diaphragm, which can effectively improve the cycle performance, the multiplying power performance and the safety performance of a lithium secondary battery comprising the composite diaphragm.
The invention also provides a preparation method of the composite diaphragm.
The invention also provides a lithium secondary battery comprising the composite diaphragm.
According to an embodiment of the first aspect of the present invention, there is provided a composite separator comprising a base layer and a functional layer arranged in superposition;
the material of the basal layer comprises cellulose; the components of the functional layer comprise PANI modified HNTs (PANI-HNTs for short, polyaniline modified halloysite nanotubes) and PEO (polyethylene oxide).
The composite diaphragm provided by the embodiment of the invention has at least the following beneficial effects:
in the functional layer, PEO is a crystalline and thermoplastic polymer, has a linear regular spiral structure, has hydroxyl groups, can be in hydrogen bond connection with substances containing carboxyl functional groups, can bond PANI-HNTs into layers as a binder, and can form hydrogen bond with a cellulose substrate layer to be tightly crosslinked to reduce interface impedance between composite membrane layers.
HNTs(Al 2 Si 2 O 5 (OH) 4 ·2H 2 O) has a nano hollow multi-wall tube structure, which is formed by dislocation and curling of aluminum oxide octahedron and silicon oxide tetrahedron lattices, wherein the inner wall of the tube is an aluminum oxide octahedron layer, the outer wall of the tube is a silicon oxide tetrahedron layer, the inner surface of the tube is an Al-OH group, the outer surface of the tube is an O-Si-O group, the surface of the tube presents electronegativity in a wide pH value range, and the active points provide possibility for wide use of halloysite. Halloysite nanotubes and Carbon Nanotubes (CNTs) have similar structural morphology and also have unique and excellent properties such as large length-diameter ratio, high strength, good corrosion resistance, good thermal conductivity, high electrical conductivity and the like. According to the invention, the HNTs are adopted to prepare the functional layer, so that a light framework (three-dimensional porous coating) can be constructed, and a rapid ion transmission channel is provided, thereby improving the ion conductivity. Can provide a channel for the full and rapid intercalation and deintercalation of the PANI and can also provide conditions for the high redox activity of the PANI grown on the surface of HNTs in situ.
The PANI of the modified HNTs has a certain capacity of accommodating active ions such as lithium ions in addition to conductivity, and when the composite separator is used for a lithium secondary battery and the positive electrode of the lithium secondary battery is in contact with the composite layer, the composite separator can not only improve the high-rate performance of the lithium secondary battery, but also improve the capacity of the obtained lithium secondary battery.
That is, the functional layer is a three-dimensional porous coating, PANI provides active sites, and HNTs provide fast ion transport channels; the lithium ion battery has the performance of conducting lithium ions and electrons, and also has the function of containing lithium ions; therefore, the lithium secondary battery comprising the composite diaphragm can be rapidly charged and discharged at high multiplying power, and has high capacity and excellent cycle performance.
The base layer is made of cellulose and is of an insulating structure, so that the composite membrane compounded by the base layer and the functional layer can still have the basic function of conducting active ions and blocking electrons.
According to some embodiments of the invention, the mass ratio of the PEO to the PANI modified HNTs in the functional layer is 1 (1-10). For example, it may be about 1:3, 1:4, 1:5, 1:8, 1:9, 2:3 or 3:7.
According to some embodiments of the invention, the composite separator has a thickness of 20-35 μm. For example, it may be specifically 23 to 28. Mu.m. And more particularly about 25 μm.
According to some embodiments of the invention, the thickness ratio of the base layer to the functional layer is 1 (0.5-2).
According to some embodiments of the invention, the thickness ratio of the base layer to the functional layer is 1 (0.8-1.2). For example, it may be about 1:1.
According to an embodiment of the second aspect of the present invention, there is provided a method for preparing the composite separator, the method comprising the steps of:
s1, preparing slurry A comprising PEO and PANI modified HNTs;
preparing a slurry B comprising cellulose;
s2, filtering the slurry A;
s3, adding the slurry B to the surface of the filter cake formed by the slurry A, and continuing filtering.
The preparation method provided by the embodiment of the invention has at least the following beneficial effects:
the preparation method provided by the invention can be realized by adopting twice filtration and simple drying, and compared with the traditional extrusion, stretching and other methods, the preparation method provided by the invention is simpler and is easy to realize.
The preparation method provided by the invention can be used for preparing the composite diaphragm, so that the capacity, the cycle performance and the multiplying power performance of a lithium secondary battery comprising the composite diaphragm can be improved to a certain extent.
According to some embodiments of the invention, in step S1, the synthesis method of PANI modified HNTs includes the following steps:
D1. preparing a solution A containing acid and aniline;
preparing a solution B containing an initiator;
preparing a dispersion liquid C containing HNTs;
D2. the solution a and the solution B were added to the dispersion C in this order, and the reaction was continued.
In the synthetic method, aniline in the solution A is polymerized in situ on the surface of HNTs under the initiation of an initiator of the solution B; the hydrogen ions of the acid in the solution A are doped into the polyaniline, so that the conductivity of the polyaniline is improved.
The conductivity of a polymer is related to its doped state, and PANI is a typical conductive polymer in terms of structure, and although pi electrons have a strong delocalization ability, the conjugated system has a limited range of movement. Only when the conjugated system is sufficiently large, the electron mobility is increased so that PANI provides free electron conduction, the chemical structure of PANI being related to conductivity. When other conditions such as oxidation degree are fixed, the conductivity of the PANI is closely related to the doping state, and the conductivity is continuously increased along with the improvement of the doping rate, and finally, the conductivity can reach about 10S/cm. When doped with an acid, it first protonates the imine nitrogen atom of the molecular chain, H as the anionic portion of the acid leaves + Transferred to the PANI molecular chain, so that the nitrogen atoms in the molecular chain are protonated and positively charged. After PANI is doped by proton acid, electron cloud rearranges, quinone ring disappears in molecular chain, positive charge on nitrogen atom is delocalized, conjugate system is gradually expanded, free electron is generated, and PANI shows conductivity.
That is, in the synthesis method, the solution A contains acid, so that the obtained polyaniline can be doped, and the conductivity of the polyaniline for modifying HNTs is remarkably improved.
In step D2 of the preparation method, the addition sequence of the solution A and the solution B is limited, so that the explosion aggregation between the solution A and the solution B is avoided, and the uniformity degree of the polyaniline deposition on HNTs is also improved.
According to some embodiments of the invention, in step D1, the HNTs are surface-treated HNTs. In particular to HNTs soaked in dodecyl trimethoxy silane aqueous solution. HNTs belong to nano particles and have a certain length-diameter ratio, but the surface of the HNTs is mainly silicon-oxygen bonds, the density of hydroxyl groups is low, the acting force of hydrogen bonds is small, and the HNTs are agglomerated in a matrix and influence of a size effect and a surface electron effect, so that the use effect of the HNTs is influenced. By adopting the method to pretreat the PANI, the adhesion difficulty of the PANI obtained in the step D2 on HNTs can be reduced, and the uniformity of dispersion can be improved.
According to some embodiments of the invention, the aqueous solution of dodecyl trimethoxy silane is a stock solution with a concentration of 93% and is an aqueous solution obtained by diluting the stock solution to 20% -40%. The use of an excess of dodecyltrimethoxysilane ensures adequate performance of the surface treatment. The surface treatment further comprises solid-liquid separation and drying after the infiltration.
According to some embodiments of the invention, the number of layers of HNTs is 15-30. For example, it may be specifically 20 to 25 layers.
According to some embodiments of the invention, the HNTs have an outer diameter of about 50nm.
According to some embodiments of the invention, the HNTs have an inner diameter of 15-20 nm.
According to some embodiments of the invention, the HNTs have a length of 100-400 nm.
According to some embodiments of the invention, in step D1, the volume to mass ratio of the acid to aniline is 1mL:1.5 g to 2g. For example, it may be about 1mL:1.8g.
According to some embodiments of the invention, in step D1, the acid comprises at least one of hydrochloric acid, sulfosalicylic acid, sulfuric acid, phosphoric acid, and hypochlorous acid.
According to some embodiments of the invention, in step D1, the acid is hydrochloric acid. The concentration of the hydrochloric acid is more than or equal to 30wt%. For example, it may be about 37wt%. Further specifically, the molar concentration may be about 12mol/L.
According to some embodiments of the invention, in step D1, the mass to volume ratio of aniline to solvent is 0.05 to 0.1g:1mL. For example, it may be about 0.07g:1mL. The solvent of the solution a includes water.
According to some embodiments of the invention, in step D1, the formulation of the solution a is performed under light-shielding conditions. For example, a tin foil can be wrapped around the formulated container.
According to some embodiments of the invention, in step D1, the formulation of the solution a comprises mixing the aniline and water, and then mixing the resulting mixture with an acid. In the process, the duration and conditions of mixing are not limited as long as sufficient mass transfer is possible. For example, the mixing time of the aniline and the water is 20-40 min; the mixing time of the obtained mixture and the acid is 10-30 min.
According to some embodiments of the invention, in step D1, the initiator comprises at least one of ammonium persulfate, hydrogen peroxide, dichromate and persulfate.
According to some embodiments of the invention, in step D1, the concentration of the initiator in the solution B is 0.1 to 0.2g/mL. For example, it may be about 0.18g/mL.
According to some embodiments of the invention, in step D1, the formulation of the solution B comprises mixing the initiator and water. The manner and duration of the mixing are not strictly limited, as long as a homogeneous solution can be formed. For example, stirring may be performed for 30 minutes. The initiator can initiate the aniline in the solution A to polymerize on the surface of HNTs.
According to some embodiments of the invention, in step D1, the solvent of the dispersion C comprises water.
According to some embodiments of the invention, in step D1, the solid content of the dispersion C is 25-35 mg/ml. For example, it may be about 30mg/ml.
According to some embodiments of the invention, in step D2, the mass ratio of aniline in the solution a to HNTs in the dispersion C is 0.4-0.6:1.
According to some embodiments of the invention, in step D2, the mass ratio of aniline in the solution a to initiator in the solution B is 1:2-3. For example, it may be about 1:2.5.
According to some embodiments of the invention, in step D2, the dispersion period is 5-15 min after adding the solution a. For example, it may be about 10 minutes.
According to some embodiments of the invention, in step D2, the temperature of the continued reaction is between 0 and 5 ℃. For example, it may be about 4 ℃.
According to some embodiments of the invention, in step D2, the duration of the continuous reaction is 20-30 hours. For example, it may be about 24 hours.
According to some embodiments of the invention, the synthesis method further comprises, after step D2, washing and drying the resulting solid product. The washing mode is water washing, and can wash off unreacted aniline and redundant H + . The drying mode comprises drying. The temperature of the drying is 50-80 ℃. For example, it may be about 60 ℃.
According to some embodiments of the invention, in the slurry a, the mass ratio of PEO to PANI modified HNTs is 1:1 to 10. For example, it may be about 1:3, 1:4, 1:5, 1:8, 1:9, 2:3 or 3:7.
According to some embodiments of the invention, the slurry a has a solids to liquid ratio of 1g: 30-80 mL. For example, 1g: 45-55 mL. The solvent of the slurry A is water.
According to some embodiments of the invention, the slurry B has a solids to liquid ratio of 1g: 30-80 mL. For example, 1g: 45-55 mL. The solvent of the slurry B is water.
According to some embodiments of the invention, the formulation of slurry B comprises grinding the mixture of cellulose and water. The duration of the grinding is 50 to 80 minutes, and may be, for example, about 60 minutes. The grinding rotating speed is 1000-1500 rpm; for example, 1030 to 1050rpm may be used. The ball-material ratio of the grinding is 45:1-55:1; for example, it may be about 50:1.
According to some embodiments of the invention, in step S2, the filtering includes vacuum filtration.
According to some embodiments of the invention, in step S2, the method further comprises performing a primary water removal treatment after the filtering. The filter cake is dried along with the filter membrane in the primary water removal mode. The degree of air drying is based on no water dripping and no warping of the filter cake. Therefore, the secondary suction filtration can be conveniently carried out.
According to some embodiments of the invention, in step S3, drying the obtained filter cake after said continuing filtering is further included. The drying mode can be determined according to the conditions available in actual production, and is not strictly and uniformly limited. The filtering mode comprises suction filtration.
In the steps S2 to S3, the amount of the slurry A or the slurry B used for filtering is determined according to the thickness of each layer in the required composite membrane, and is not uniformly limited.
According to an embodiment of the third aspect of the present invention, there is provided an alkali metal secondary battery including a battery cell including a positive electrode, the composite separator, and a negative electrode, which are stacked in this order; in the composite separator, the functional layer is in contact with the positive electrode.
The alkali metal secondary battery provided by the invention has at least the following beneficial effects:
compared with an alkali metal secondary battery comprising a conventional diaphragm, the alkali metal secondary battery provided by the invention has higher discharge capacity, initial efficiency and cycle performance, and is more suitable for high-rate charge and discharge; wherein:
in the charging process, active ions in the positive electrode migrate to the negative electrode, and in the discharging process, the active ions from the negative electrode can be embedded into not only the positive electrode material but also the PANI of the composite diaphragm, so that the discharge gram specific capacity and the first efficiency (more than 100%) of the alkali metal secondary battery are improved.
In the charge-discharge process, the reversible reaction of PANI in the composite layer is shown as follows:
P+A←→P+A + +e - ；
wherein P is PANI and A is an anion. During charging, anions in the electrolyte move to the positive electrode to perform oxidation doping reaction with PANI, so that conductivity can be improved, and Li is simultaneously + And other alkali metal active ions move to the negative electrode and are reduced and separated out on the surface of the negative electrode, electrons flow into the negative electrode from the positive electrode through an external circuit, and the discharge state is the reverse process.
PANI can be represented by a copolymer of quinone diimine and phenylenediamine, the degree of redox of which is represented by the y value. When the y values are different, the structure, composition and conductivity are also different. When y=1 is a fully reduced full-benzene structure, y=0 is a "benzene-quinone" alternating structure, all being insulators. And y=0.5 is a half oxidation and reduction structure with a benzoquinone ratio of 3:1, and the corresponding eigenstate, namely the original state of the polyaniline obtained by the invention, is green in color; this state changes as charge and discharge proceeds. Polyaniline with different oxidation degrees shows different components, structures, colors and conductivity characteristics. During the transition from the fully reduced state (y=1) to the fully oxidized state (y=0), the polyaniline appears yellow, green, deep blue, deep purple and black in sequence as the oxidation degree increases. Due to the change of the oxidation state of PANI in the charge and discharge process, all layers of the diaphragm are of insulating structures under the conditions of full power, no power storage and the like, and the safety of the alkali metal secondary battery is further improved.
According to some embodiments of the invention, the alkali metal secondary battery includes at least one of a lithium secondary battery, a sodium secondary battery, and a potassium secondary battery. Further specifically, the negative electrode of the alkali metal secondary battery includes an alkali metal simple substance.
According to some embodiments of the invention, the alkali metal secondary battery is a fast-charge alkali metal secondary battery.
According to some embodiments of the invention, the lithium secondary battery is a fast-charge lithium secondary battery.
In the lithium secondary battery:
according to some embodiments of the invention, in the positive electrode, the positive electrode active material includes at least one of lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide.
According to some embodiments of the invention, in the anode, the anode active material includes at least one of graphite and porous carbon.
According to some embodiments of the invention, the lithium secondary battery includes at least one of a half battery and a full battery. The half cell is a cell using metallic lithium as a negative electrode active material.
According to some embodiments of the invention, the lithium secondary battery includes at least one of a button battery, a pouch battery, a cylindrical battery, and a square-case battery.
If not specified, the fast-charging alkali metal secondary battery is an alkali metal secondary battery which can be charged and discharged with a rate of 3C or more, for example, 5C and maintains good cycle performance.
When the positive electrode active material is lithium iron phosphate and the negative electrode active material is metal lithium and the charge-discharge multiplying power is 1C, the lithium secondary battery comprising the composite diaphragm has the discharge capacity of being more than or equal to 51mAh/g compared with the lithium secondary battery comprising the traditional diaphragm.
The term "about" as used herein, unless otherwise specified, means that the tolerance is within + -2%, for example, about 100 is actually 100 + -2%. Times.100.
Unless otherwise specified, the term "between … …" in the present invention includes the present number, for example "between 2 and 3" includes the end values of 2 and 3.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic structural view of a composite separator according to example 1 of the present invention.
Fig. 2 is a schematic partial cross-sectional view of a button cell obtained in accordance with an embodiment of the present invention.
Fig. 3 is a graph of the magnification results of the button cell including example 1 and comparative example 1.
FIG. 4 is a schematic diagram of the structure of polyaniline obtained by polymerization in preparation example of the material of the present invention.
Reference numerals:
100. a composite membrane; 110. a functional layer; 111. PANI-HNTs; 112. PEO; 120. a base layer; 200. a positive electrode; 300. and a negative electrode.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Material preparation example 1
The PANI-HNTs hybrid material is synthesized by the method, which comprises the following specific steps:
D1. in a light-shielding environment, 3.72g of ANI is sucked and weighed by a syringe and added into a 200mL beaker, and the outside of the beaker is wrapped with tinfoil to be light-shielding; putting a stirrer into the beaker, adding 50mL of deionized water, and stirring on the stirrer for 30min; sucking 2mL of concentrated hydrochloric acid (37 wt%) and pouring into the beaker, stirring for 20min to obtain a solution A;
another 100mL beaker is taken, 9.12g of ammonium persulfate is weighed, 50mL of deionized water is added, and stirring is carried out for 30min to fully dissolve, thus obtaining solution B;
and taking a 100mL beaker, weighing 3g of HNTs, adding water, stirring for 30min, and carrying out ultrasonic treatment for 10min to uniformly mix, thereby obtaining a dispersion liquid C with the solid content of about 30mg/mL.
Wherein HNTs are stirred and mixed with the dodecyl trimethoxy silane aqueous solution before being used, then solid-liquid separation is carried out, and the mixture is dried. The solute of the aqueous solution of dodecyl trimethoxy silane was 27.9% based on the mass of the solution.
The HNTs are formed by curling 20 sheets, the outer diameter is about 50nm, the inner diameter is 15-20 nm, and the length is 100-400 nm. In practical production, it is impossible to obtain a single particle diameter, and the parameters such as the inner diameter and the length are distributed within the above-mentioned range.
D2. 20mL of the solution A was sucked up and added to the dispersion C, and after stirring for 10min, 20mL of the solution B was added.
Refrigerating the mixture in a refrigerator at 4 ℃ for 24 hours; polyaniline is polymerized on the surface of HNTs in situ, and the structure of polyaniline is shown in figure 4.
D3. Repeatedly centrifuging and washing the solid product obtained in the step D2 by deionized water to remove polyaniline and redundant H on the surface + 。
And (3) drying the prepared mixture in a hot table at 60 ℃, and sealing, collecting and storing the mixture by using a self-sealing bag.
Material preparation example 2
The synthesis of the PANI-HNTs hybrid material comprises the following specific steps and the difference of the material preparation example 1: in the step D2, 20mL of the solution A and 20mL of the solution B are simultaneously sucked, and are simultaneously added into the dispersion liquid C, and the mixture is stirred for 10 min; refrigeration was performed as in example 1.
Material preparation example 3
The synthesis of the PANI-HNTs hybrid material comprises the following specific steps and the difference of the material preparation example 1:
in the preparation of the solution A in the step D1, hydrochloric acid is not added.
Example 1
The composite diaphragm is prepared by the method and comprises the following specific steps:
s1, preparing raw materials:
formulation of slurry a (containing PEO and PANI-HNTs):
first, 0.4g PEO was poured into a beaker, then 1.6g PANI-HNTs powder (from Material preparation example 1) was weighed, and 100mL deionized water was added to prepare a mixed slurry of PEO and PANI-HNTs in a solid-to-liquid ratio of 20mg/mL, referred to as slurry A.
Slurry B (including cellulose) was formulated:
weigh 2g of cellulose and add 100mL deionized water in a ball mill pot at a ball to charge ratio of 50:1 ball milling for 1h at the rotating speed of 1032r/min, and collecting for later use, namely slurry B.
S2, performing suction filtration by using a vacuum suction filtration device, wherein a filter membrane is 1.2 microns in pore diameter, pouring 20mL of slurry A, and preparing a film (a functional layer) with the thickness of about 12.5 microns. The thickness is used as the standard in the step, and the dosage of the slurry A is changed according to the size of the filter membrane.
S3, after the film obtained in the step S2 is dried to be semi-dry (the film can be dried within the time range from no water dripping to no warping), 12mL of slurry B is poured into the film to be filtered, and a basal layer is formed on one side surface of the functional layer. The usage amount of the slurry B in the step is the same as the usage amount of the slurry A in the step S2, and the adjustment is carried out according to the area of the obtained composite diaphragm.
After drying, a composite membrane with a thickness of about 25 μm is obtained, which is cut into a disc with a diameter of 19mm by a slicer (for assembling button cells, if a soft package cell is to be assembled, etc., the size of the cut-out is to be adjusted), and the disc is put into a self-sealing bag and put into a dryer for standby.
Before the composite diaphragm is used, the composite diaphragm needs to be dried for 2 hours at the temperature of 100 ℃ to remove residual moisture.
The structural schematic diagram of the composite separator 100 obtained in this example is shown in fig. 1, and specifically includes a substrate layer 120 and a functional layer 110 that are disposed in a superimposed manner, where the functional layer includes PEO 112 and PANI-HNTs 111 distributed in the PEO 112.
Example 2
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 1:9 (the sum of the masses was kept unchanged).
Example 3
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 3:7 (the sum of the masses was kept unchanged).
Example 4
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 2:3 (the sum of the masses was kept unchanged).
Example 5
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 1:1 (the sum of the masses was kept unchanged).
Example 6
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 1:10 (the sum of the masses was kept unchanged).
Example 7
This example produced a composite separator, which differs from example 1 in that:
in this example, the thickness of the cellulose substrate and the functional layer was 2:1 (the sum of the thicknesses of both was kept constant at 25 μm).
Example 8
This example produced a composite separator, which differs from example 1 in that:
in this example, the thicknesses of the cellulose substrate and the functional layer were 1:2 (the sum of the thicknesses of both was kept constant at 25 μm).
Example 9
This example produced a composite separator, which differs from example 1 in that:
in this example, the thicknesses of the cellulose substrate and the functional layer were 1:0.8 (the sum of the thicknesses of both was kept constant at 25 μm).
Example 10
This example produced a composite separator, which differs from example 1 in that:
in this example, the thicknesses of the cellulose substrate and the functional layer were 1:1.2 (the sum of the thicknesses of both was kept constant at 25 μm).
Example 11
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 7:3 (the sum of the masses was kept unchanged).
Example 12
This example produced a composite separator, which differs from example 1 in that:
in this example, the mass ratio of PEO to PANI-HNTs was 1:11 (the sum of the masses was kept unchanged).
Comparative example 1
This example produced a separator, which differs from example 1 in that:
the resulting separator was two cellulose layers (substrate layers), contained no functional layers, and the total thickness was the same as that of the composite separator obtained in example 1.
The preparation method of this example refers to the preparation method of example 1, specifically:
the preparation of the slurry A is not included in the step S1; in step S2, 20mL of slurry A is replaced with 12mL of slurry B; the procedure is as in example 1.
Comparative example 2
This example produced a separator, which differs from example 1 in that:
the resulting separator was a two-layer functional layer, without a base layer, and the total thickness was the same as that of the composite separator obtained in example 1.
The preparation method of this example refers to the preparation method of example 1, specifically:
the preparation of the slurry B is not included in the step S1; in step S3, 12mL of slurry B is replaced with 20mL of slurry A; the procedure is as in example 1.
Comparative example 3
This example produced a separator, which differs from example 1 in that:
in slurry A, PANI-HNTs were replaced with equal amounts of PANI.
The preparation method of PANI and the preparation example of the material are different in that: HNTs were not added to dispersion C.
Comparative example 4
This example provides a diaphragm, specifically:
coating a polyolefin membrane surface with a coating comprising PVDF and Al 2 O 3 Is a dispersion of (a). Wherein PVDF and Al 2 O 3 The mass ratio of (2) was 7:3, the base film thickness was 25 μm, and the coating thickness was 3. Mu.m.
Comparative example 5
This example produced a composite separator, which differs from example 1 in that:
PANI-HNTs were used from material preparation 2.
Comparative example 6
This example produced a composite separator, which differs from example 1 in that:
PANI-HNTs were used from material preparation 3.
Application example
This example provides a button cell. The structure of the button cell obtained in this example is shown in fig. 2, and the battery core of the button cell includes a positive electrode 200, a composite diaphragm 100 and a negative electrode 300 which are stacked; the functional layer 110 of the composite separator 100 faces the positive electrode 200. Wherein the material of the negative electrode 300 is lithium metal; the positive active material of the positive electrode 200 is lithium iron phosphate.
Test case
The electrochemical performance of the button cell obtained in the application example is tested, the specific test voltage is 2.5V-4.2V, and the gram specific capacity is 170mAh/g; respectively performing a 1C cycle test, a 3C cycle test and a 5C cycle test; the capacities after 1C first week and 300 weeks of circulation, and the capacities after 3C and 5C first week and 100 weeks of circulation were counted; the test results are shown in tables 1 to 3. This example also tested the rate performance of the coin cell at 0.05C, 0.2C, 0.5C, 1C, 3C, 5C, 0.5C and 0.2C.
Table 1 capacity of 300 cycles under button cell 1C
TABLE 2 capacity for 100 cycle at 3C of button cell
| Sample of | First week discharge capacity | Discharge capacity of 100 weeks |
| Example 1 | 167.3mAh/g | 165.2mAh/g |
| Example 2 | 160.3mAh/g | 158.1mAh/g |
| Example 3 | 169.2mAh/g | 166.3mAh/g |
| Example 4 | 163.7mAh/g | 163.5mAh/g |
| Example 5 | 144.1mAh/g | 142.9mAh/g |
| Example 6 | 162.6mAh/g | 135mAh/g |
| Example 7 | 136.7mAh/g | 125.6mAh/g |
| Example 8 | 169.4mAh/g | 127.3mAh/g |
| Comparative example 1 | 111.8mAh/g | 110.6mAh/g |
| Comparative example 3 | 127.7mAh/g | 124.8mAh/g |
TABLE 3 capacities (mAh/g) of button cells after 100 weeks at different magnifications
| Sample of | 0.2C | 0.5C | 1C | 3C | 5C |
| Example 1 | 210.6 | 196.7 | 182.6 | 165.2 | 132.6 |
| Comparative example 1 | 158.1 | 138.6 | 128.5 | 110.6 | 85.3 |
| Comparative example 3 | 163.4 | 155.6 | 141.4 | 124.8 | 109.1 |
In the cycling results:
as can be seen from comparative examples 1 and comparative examples 1 to 3, the composite separator provided by the present invention can improve the capacity and cycle performance of the lithium secondary battery in both the conventional rate (1C) and the high rate (3C), specifically, after 300 weeks of 1C cycle, the difference between the capacities of example 1 and comparative example 1 is > 50mAh/g, and after 100 weeks of 5C cycle, the capacity of example 1 is 132.6mAh/g; the capacity of comparative example 1 was 85.3mAh/g. This is mainly because PANI serves as a place for lithium ions to intercalate and deintercalate during charge and discharge, and the remaining structure provides a stable and firm channel for lithium ion shuttling. The electrochemical properties, particularly the capacity and cycle properties at high rates, are degraded if the structure of the composite separator and the composition of the functional layer (comparative examples 1 to 3) are changed in the present invention; for example, in comparative example 3, the fast ion channel provided by HNTs is absent, the cycle performance, particularly at high magnification, is significantly reduced, for example, in comparative example 2, two functional layers are used without a base layer capable of isolating electron conduction, and thus the separator cannot be objectively provided, which may cause a short circuit between the positive electrode and the negative electrode, and electrochemical performance detection is not performed in view of safety and the like.
As is clear from comparative examples 1 to 6 and examples 11 to 12, the mass ratio of PEO to PANI-HNTs in the functional layer affects the electrochemical performance of the resulting composite separator to some extent, and in particular, as the PANI-HNTs ratio increases, the electrochemical performance of the composite separator tends to increase and decrease, mainly because the adhesiveness between the functional layer and the base layer and the structural stability of the functional layer decrease when the PEO content is too low, and the PANI-HNTs drop off, whereas if the PEO content is too high, the substances capable of containing lithium ions and reacting with lithium ions in the composite separator decrease, and thus the capacity decreases.
As is clear from comparative example 1 and examples 7 to 10, when the thickness of the cellulose substrate is too thin, the composite separator battery has poor cycle stability, and the cellulose substrate has poor electronic insulation during long cycles, resulting in micro short circuit of the separator and thus capacity decrease; when the thickness of the cellulose substrate is too thick, the active sites PANI in the functional layer become smaller, and the capacity provided additionally becomes smaller, so that it is not the optimal solution.
The results of comparative examples and comparative example 4 show that the PVDF/AL is commercially available at present 2 O 3 Compared with a coated polyolefin diaphragm battery, the capacity of the composite diaphragm battery provided by the invention still keeps up to 181.6mAh/g after 300 cycles are cycled at 1C multiplying power. Compared with the conventional commercial diaphragm, the composite diaphragm provided by the invention has the advantage that the electrochemical performance is greatly improved.
The results of comparative examples 1 and 5 show that, since ammonium persulfate in solution B and aniline in solution a can react rapidly, if aniline cannot be mixed with HNTs sufficiently due to simultaneous addition of solution B and solution a to solution C, the prepared PANI will agglomerate and be unevenly distributed on the surface of HNTs, which affects electrochemical performance.
As is clear from the results of comparative examples 1 and 6, the absence of hydrochloric acid in the preparation of PANI-HNTs results in the preparation of PANI having low redox properties and being not Li + Providing attachment points during charge and discharge, thereby affecting electrochemical performance.
The multiplying power test result shows that: the composite diaphragm cell provided by the embodiment 1 of the invention has discharge specific capacities of 165.2mAh/g and 132.6mAh/g respectively after being circulated for 100 weeks under the multiplying power of 3C and 5C, and can provide enough lithium ions for high-multiplying power charge and discharge mainly because PEO swells in electrolyte; in contrast, in comparative example 1, the separator formed of a plurality of layers of cellulose had a capacity lower than that of example 1 at each magnification. This also shows that the composite diaphragm provided by the invention has the functions of capacity improvement and suitability for high-rate charge and discharge (quick charge and quick discharge). The specific test results are shown in fig. 3.
In conclusion, the composite diaphragm provided by the invention can improve the capacity and the cycle performance of the lithium secondary battery through the design of the structure and the components, and is suitable for high-rate charge and discharge. The lithium secondary battery comprising the composite diaphragm can be charged quickly, and is expected to be widely applied to power batteries, energy storage batteries and 3C small household electrical appliance batteries.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Claims (10)
1. A composite membrane, characterized in that the composite membrane comprises a basal layer and a functional layer which are overlapped;
the material of the basal layer comprises cellulose; the components of the functional layer include PANI modified HNTs and PEO.
2. The composite separator of claim 1, wherein the mass ratio of PEO to PANI modified HNTs in the functional layer is from 1:1 to 1:10.
3. The composite separator of claim 1, wherein the thickness ratio of the base layer to the functional layer is 1:0.5-1:2.
4. The composite membrane of claim 1, wherein the composite membrane has a thickness of 20 to 35 μm.
5. A method of producing the composite separator according to any one of claims 1 to 4, comprising the steps of:
s1, preparing slurry A comprising PEO and PANI modified HNTs;
preparing a slurry B comprising cellulose;
s2, filtering the slurry A;
s3, adding the slurry B to the surface of the filter cake formed by the slurry A, and continuing filtering.
6. The preparation method according to claim 5, wherein in step S1, the synthesis method of PANI modified HNTs comprises the following steps:
D1. preparing a solution A containing acid and aniline;
preparing a solution B containing an initiator;
preparing a dispersion liquid C containing HNTs;
D2. the solution a and the solution B were added to the dispersion C in this order, and the reaction was continued.
7. The method according to claim 6, wherein in the step D2, the mass ratio of the aniline in the solution A to HNTs in the dispersion C is 0.4:1 to 0.6:1; and/or, in the step D1, the volume-to-mass ratio of the acid to the aniline is 1mL:1.5 g to 2g.
8. The method according to claim 6, wherein in step D2, the temperature of the continuous reaction is 0 to 5 ℃; and/or the duration of the continuous reaction is 20-30 h.
9. An alkali metal secondary battery is characterized by comprising a battery core, wherein the battery core comprises a positive electrode, a composite diaphragm and a negative electrode which are sequentially overlapped; in the composite separator, the functional layer is in contact with the positive electrode.
10. The alkali metal secondary battery according to claim 9, wherein the alkali metal secondary battery is a fast-charge alkali metal secondary battery; and/or the alkali metal secondary battery includes at least one of a lithium secondary battery, a sodium secondary battery, and a potassium secondary battery.
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