CN117638406A - Modified diaphragm for lithium metal battery and preparation method thereof - Google Patents
Modified diaphragm for lithium metal battery and preparation method thereof Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 58
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 9
- 238000000576 coating method Methods 0.000 claims abstract description 7
- 238000005275 alloying Methods 0.000 claims abstract description 6
- 239000011248 coating agent Substances 0.000 claims abstract description 5
- 239000000843 powder Substances 0.000 claims description 24
- -1 polyethylene Polymers 0.000 claims description 22
- 239000004743 Polypropylene Substances 0.000 claims description 20
- 239000012528 membrane Substances 0.000 claims description 20
- 229920001155 polypropylene Polymers 0.000 claims description 20
- 239000002243 precursor Substances 0.000 claims description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000004698 Polyethylene Substances 0.000 claims description 6
- 239000002270 dispersing agent Substances 0.000 claims description 6
- 229920000573 polyethylene Polymers 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- 229910000314 transition metal oxide Inorganic materials 0.000 claims description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- 229910000733 Li alloy Inorganic materials 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 3
- 229910001947 lithium oxide Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052797 bismuth Inorganic materials 0.000 claims description 2
- 229910052796 boron Inorganic materials 0.000 claims description 2
- 239000001913 cellulose Substances 0.000 claims description 2
- 229920002678 cellulose Polymers 0.000 claims description 2
- 239000000919 ceramic Substances 0.000 claims description 2
- 239000011521 glass Substances 0.000 claims description 2
- 229910052738 indium Inorganic materials 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002105 nanoparticle Substances 0.000 claims description 2
- 239000004745 nonwoven fabric Substances 0.000 claims description 2
- 229920000642 polymer Polymers 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 230000002194 synthesizing effect Effects 0.000 claims description 2
- 229910052723 transition metal Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 4
- 229910018068 Li 2 O Inorganic materials 0.000 claims 1
- 229910052742 iron Inorganic materials 0.000 claims 1
- 229910044991 metal oxide Inorganic materials 0.000 claims 1
- 150000004706 metal oxides Chemical class 0.000 claims 1
- 239000010410 layer Substances 0.000 abstract description 18
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 11
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 11
- 230000008021 deposition Effects 0.000 abstract description 8
- 230000005012 migration Effects 0.000 abstract description 7
- 238000013508 migration Methods 0.000 abstract description 7
- 230000004907 flux Effects 0.000 abstract description 5
- 238000011065 in-situ storage Methods 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 2
- 230000008595 infiltration Effects 0.000 abstract 1
- 238000001764 infiltration Methods 0.000 abstract 1
- 239000002346 layers by function Substances 0.000 abstract 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 210000004027 cell Anatomy 0.000 description 9
- 210000001787 dendrite Anatomy 0.000 description 9
- 239000003792 electrolyte Substances 0.000 description 8
- 229910013553 LiNO Inorganic materials 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 229910010710 LiFePO Inorganic materials 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 239000007784 solid electrolyte Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 3
- 229910006270 Li—Li Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000001989 lithium alloy Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 238000009841 combustion method Methods 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
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- 238000010438 heat treatment Methods 0.000 description 2
- 238000001453 impedance spectrum Methods 0.000 description 2
- 238000000155 in situ X-ray diffraction Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000009827 uniform distribution Methods 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- YASYEJJMZJALEJ-UHFFFAOYSA-N Citric acid monohydrate Chemical compound O.OC(=O)CC(O)(C(O)=O)CC(O)=O YASYEJJMZJALEJ-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 1
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910000416 bismuth oxide Inorganic materials 0.000 description 1
- FBXVOTBTGXARNA-UHFFFAOYSA-N bismuth;trinitrate;pentahydrate Chemical compound O.O.O.O.O.[Bi+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FBXVOTBTGXARNA-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000002134 carbon nanofiber Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 229960002303 citric acid monohydrate Drugs 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- OPHUWKNKFYBPDR-UHFFFAOYSA-N copper lithium Chemical compound [Li].[Cu] OPHUWKNKFYBPDR-UHFFFAOYSA-N 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- TYIXMATWDRGMPF-UHFFFAOYSA-N dibismuth;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Bi+3].[Bi+3] TYIXMATWDRGMPF-UHFFFAOYSA-N 0.000 description 1
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 description 1
- 230000008034 disappearance Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011066 ex-situ storage Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000002186 photoelectron spectrum Methods 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 229910001251 solid state electrolyte alloy Inorganic materials 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- QBAZWXKSCUESGU-UHFFFAOYSA-N yttrium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Y+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QBAZWXKSCUESGU-UHFFFAOYSA-N 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
Abstract
The invention provides a modified diaphragm for a lithium metal battery and a preparation method thereof, wherein the modified diaphragm has the capability of carrying out conversion-alloying reaction with a lithium metal anode, so that a multifunctional intermediate layer is generated in situ, and the functional layer has the effects of homogenizing lithium ion flux, improving the migration number of lithium ions and improving the infiltration performance and mechanical strength of the diaphragm. According to the method, the functional components with unstable air are introduced into the lithium metal battery through a simple diaphragm coating means, so that dendrite-free deposition of the anode is realized, and the cycle life and the safety performance of the lithium metal battery are greatly improved.
Description
Technical Field
The invention belongs to the technical field related to lithium metal batteries, and particularly relates to a lithium metal battery modified diaphragm, a preparation method and application thereof.
Background
The growing market for portable electronics and electric vehicles has greatly affected the technological revolution of Lithium Batteries (LBs), moving them towards higher energy densities. Metallic lithium due to itLow density (0.53 g cm) -3 ) High theoretical specific capacity (3860 mAh g) -1 ) And low redox potential (-3.040V compared to standard hydrogen electrode) are considered ideal negative electrodes for next generation high energy density battery systems. However, problems such as volume expansion of the negative electrode, cracking of the solid electrolyte interface layer, dendrite growth caused by uneven deposition and the like occur in the lithium deposition process, and problems such as generation of dead lithium and repair of the solid electrolyte interface layer occur in the lithium stripping process, so that the lithium metal battery has a short cycle life. Worse still, uncontrolled lithium dendrites can puncture the separator to short, causing a series of safety hazards, which are critical issues limiting lithium metal battery industrialization.
Currently, most of researches for solving the application problem of lithium metal negative electrodes are focused on electrolyte regulation, design of three-dimensional current collectors, diaphragm modification, use of solid electrolytes, and the like. The use of additives in the electrolyte may form artificial solid electrolyte interface layers, but the long-term nature of this strategy remains to be verified as the additives are consumed. Designing a three-dimensional current collector for lithium metal can reduce the local current density, thereby inhibiting the growth of lithium dendrites, but inevitably reduces the actual energy density of the battery. Solid state electrolytes are continually being explored due to their lower ionic conductivity and poor interfacial contact.
The separator, which is an integral part of the battery, has a great influence on the performance of the battery. In particular, in lithium metal batteries, commercial separators have an uneven pore structure, which in turn results in uneven lithium flux distribution, which in turn leads to lithium dendrite growth. Therefore, modification of the separator to homogenize the lithium flux is an important measure for suppressing lithium dendrites.
Disclosure of Invention
The invention aims to provide a modified diaphragm for a lithium metal battery and a preparation method thereof, which can realize uniform deposition of lithium and solve the problem of lithium dendrite existing in the lithium metal battery.
The invention provides a modified diaphragm for a lithium metal battery, wherein a modified layer is arranged on the surface of the diaphragm, the modified layer of the diaphragm can spontaneously react with lithium metal in situ through simple physical contact or electrochemical process, the in situ reaction can be divided into two steps of conversion reaction and alloying reaction, and finally a multifunctional intermediate layer consisting of transition metal oxide, lithium alloy and lithium oxide is formed. The intermediate layer has the important functions of regulating the uniform distribution of lithium ion flux, improving the migration number of lithium ions and improving the wettability and mechanical strength of the diaphragm, so that the cycle life of the lithium metal battery is greatly prolonged.
The modified layer is made of inorganic nano ceramic powder, and the chemical general formula is A (+m) x B (+n) y O z (0<x/y is equal to or less than 4, z=0.5 (mx+ny)), wherein: a is a transition metal element, the valence state of the element is +m, and the element specifically comprises at least one of La, Y, fe and the like; b is a main group metal element, the valence state of the element is +n, and the element specifically comprises at least one of In, sn, sb, bi and other elements.
The invention also provides a preparation method of the modified diaphragm, which comprises the following steps:
step 1, synthesizing A x B y O z Precursor powder;
step 2, dispersing the precursor powder in a dispersing agent, and performing sanding treatment to obtain nano-sized finished product powder;
and step 3, uniformly mixing the finished powder with the high polymer solution, coating the mixture on the surface of the diaphragm, and drying to obtain the modified diaphragm.
Further, in step 2: the dispersing agent is at least one of water, ethanol and acetone, preferably ethanol; the mass fraction of the precursor powder dispersed in the dispersing agent is 5% -25%, preferably 10%.
Further, in the step 2, the rotational speed of the sanding treatment is 2000-3000 r min -1 Preferably 2400r min -1 The method comprises the steps of carrying out a first treatment on the surface of the The sanding time is 20 to 120min, preferably 40min.
Further, in the step 3, the membrane is at least one of a polyethylene membrane, a polypropylene membrane, a polyethylene/polypropylene/polyethylene three-layer membrane, a glass cellulose membrane and a non-woven fabric membrane.
Further, the separator modification layer has a thickness of 1 to 20 μm.
The synthesis scheme of the precursor powder is not particularly limited, and any of solid phase method, coprecipitation method, combustion method, etc. known to those skilled in the art may be used, and the combustion method is preferable.
The coating method of the present invention is not particularly limited, and coating methods known to those skilled in the art may be used, and blade coating is preferable.
Compared with the prior art, the invention has the beneficial effects that:
1. the method provides a lithium metal battery modified diaphragm which has reactivity with lithium metal and can generate a multifunctional intermediate layer consisting of transition metal oxide, lithium alloy and lithium oxide in situ through conversion-alloying reaction. The intermediate layer has the important functions of regulating the uniform distribution of lithium ion flux, improving the migration number of lithium ions and improving the wettability and mechanical strength of the diaphragm, so that the cycle life of the lithium metal battery is greatly prolonged.
2. According to the method, the functional composition of unstable air is introduced into the lithium metal battery through a simple diaphragm coating means, so that dendrite-free deposition of lithium is realized, and the cycle life and the safety performance of the lithium metal battery are greatly improved. Meanwhile, the preparation process of the modified diaphragm is simple, the mass is light, and the influence on the actual energy density of the battery is small.
Drawings
Fig. 1 is a scanning electron microscope (a, b) and an X-ray diffraction pattern (c) of the precursor powder and the final powder in example 1.
FIG. 2 is a scanning electron microscope image of the surface (a) and the cross section (b) of the modified separator in example 2.
FIG. 3 is a photograph of a separator before (a), after (b), and after (c, d) the modification in example 3.
FIG. 4 is an in situ X-ray diffraction pattern (a) and an ex situ X-ray photoelectron spectrum (b) of the modified separator of example 4 reacted with lithium metal.
Fig. 5 is a deposition profile of lithium metal in a lithium copper half-cell using commercial polypropylene separator (a) and modified separator (b) in example 5.
FIG. 6 is a graph showing the results of measurement of the migration number of lithium ions using the commercial polypropylene separator (a) and the modified separator (b) in example 6, and the graph showing the electrochemical impedance spectra before and after polarization.
FIG. 7 is Li-LiFePO using a commercial Polypropylene separator and a modified separator in example 7 4 The rate (a) and cycle performance (b) of the battery.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. However, the drawings and examples do not constitute a limitation of the present invention. This invention may be embodied in many different forms and is not limited to the embodiments described herein.
Example 1
Dissolving yttrium nitrate hexahydrate and bismuth nitrate pentahydrate in dilute nitric acid with the pH value of 2 according to the molar ratio of 1:3, adding citric acid monohydrate with the same molar quantity as metal ions, adjusting the pH value to 7 by ammonia water, stirring and heating the uniformly mixed solution until combustion reaction occurs, and heating the product at the temperature of 700 ℃ for 3 hours under the air atmosphere to obtain precursor powder. Dispersing 10% precursor powder in 2400r min ethanol -1 Sanding for 40min at the rotating speed to obtain the finished powder. And carrying out electron microscope scanning and X-ray diffraction on the precursor powder and the finished powder.
FIG. 1 shows electron microscope scans (a, b) and X-ray diffraction patterns (c) of the precursor powder and the final powder prepared in example 1 of the present invention, which can be seen to successfully prepare nanoparticle-sized A x B y O z (A：Y，B：Bi，x＝0.5，y＝1.5，z＝3)。
Example 2
Mixing iridium-stabilized bismuth oxide powder prepared in example 1, poly (vinylidene fluoride-co-hexafluoropropylene) and N-methylpyrrolidone according to a mass ratio of 1:0.15:3, and ball milling and stirring for 0.5h to obtain mixed slurry; the slurry is coated on a commercial polypropylene diaphragm in a scraping way, and is put into an oven at 80 ℃ to be dried for 12 hours, so as to obtain a modified diaphragm, and a wafer with the diameter of 16mm is punched for standby. The membrane was subjected to electron microscope scanning, and as a result, as shown in FIG. 2, it was found that the membrane-modified layer was relatively dense and flat, and had a thickness of about 7. Mu.m.
Example 3
This example shows the optical photographs before and after membrane modification and before and after reaction.
Lithium metal is used as an anode and a cathode, and 1M LiTFSIDME/DOL (volume ratio is 1:1) is added with 2% of LiNO by mass fraction 3 As an electrolyte, a Li-Li symmetric battery was assembled using the modified separator in example 2. 0.05mAcm -2 After 50 constant current cycles at current density, the cell was disassembled in an argon glove box, the membrane was rinsed with DME, and an optical photograph of both sides of the membrane after the reaction was taken, and compared with the original commercial polypropylene membrane, the modified membrane in example 2.
As a result, see fig. 3, the commercial polypropylene separator was a white disc (a), the modified separator in example 2 exhibited a pale yellow (b) of the modified layer, and became black (c) after the reaction, and the unmodified side maintained the white (d) of the commercial polypropylene separator.
Example 4
This example explores the product of the transformation-alloying reaction between the finishing layer and lithium metal.
LiNO with lithium metal as a negative electrode, beryllium window as a positive electrode, 1M LiTFSIDME/DOL (volume ratio of 1:1) added with 2% mass fraction 3 As an electrolyte, a Li-Be half cell was assembled in an argon glove box using the modified separator in example 2, and the phase change (a) of the separator modified layer during the first discharge charge cycle was observed in situ. Further, with lithium metal as the anode and cathode, 1MLiTFSIDME/DOL (volume ratio of 1:1) plus 2% LiNO by mass fraction 3 As an electrolyte, a Li-Li symmetric battery was assembled using the modified separator in example 2. 0.05mA cm -2 And (3) after 50 times of constant current circulation under the current density, disassembling the battery in an argon glove box, flushing the electrode plate by using DME, and performing X-ray photoelectron spectroscopy test (b) on the diaphragm modified layer after drying.
FIG. 4 is a characterization of the reaction product of the modified separator and lithium metal of example 4, in situ X-ray diffraction pattern (a) showing the gradual disappearance of YSB peak sites, the rapid appearance of Bi peak sites and the subsequent conversion to Li as the discharge proceeds 3 Bi corresponds to the peak position, confirming the occurrence of the conversion-alloying reaction. X-rayThe photoelectron spectrum (b) detects Li 3 Bi and Y 2 O 3 The signal further demonstrates that the reaction product is a transition metal oxide (here Y 2 O 3 ) Lithium alloy (here Li 3 Bi) and lithium oxide (Li 2 O)。
Example 5
This example compares the effect of modified and commercial polypropylene separators on lithium deposition morphology.
Lithium metal is used as a negative electrode, copper foil is used as a positive electrode, and 1M LiTFSIDME/DOL (volume ratio is 1:1) is added with 2% of LiNO by mass fraction 3 For the electrolyte, a Li-Cu half cell was assembled using the modified separator and the commercial polypropylene separator in example 2, respectively. Constant current discharge is carried out on the Li-Cu half cell, and the current density is 1mAcm -2 The discharge time was 3h, at which time 3mAh cm was deposited on the copper foil -2 Is a lithium metal of (a). The cell was disassembled in an argon glove box, the electrode sheet was rinsed with DME, and after drying, scanning electron microscopy was performed. The results are shown in FIG. 5.
Fig. 5 is a deposition morphology of lithium in example 5, in contrast to a cell using a modified separator, where the deposited lithium exhibited a tight and smooth surface, demonstrating that the modified separator facilitates suppression of lithium dendrites.
Example 6
This example tests lithium ion migration numbers based on modified separator and commercial polypropylene separator.
Lithium metal is used as an anode and a cathode, and 1M LiTFSIDME/DOL (volume ratio is 1:1) is added with 2% of LiNO by mass fraction 3 For the electrolyte, a Li-Li symmetric battery was assembled using the modified separator and the commercial polypropylene separator in example 2, respectively. The current-time response curve at a polarization voltage of 10mV was tested for electrochemical impedance spectra before and after polarization. The lithium ion migration number was calculated by the following formula:
wherein I is s Is steady state current, I o For initial current, ΔV is the DC polarization voltage pulse (10 mV), R o And R is s Initial and steady state interface resistances, respectively.
Fig. 6 is a lithium ion mobility test result in example 6. Thanks to the transition metal oxide (corresponding here to Y 2 O 3 ) Adsorption of anions increased the lithium ion mobility from 0.37 for commercial polypropylene membranes to 0.79 for modified membranes. The nucleation and growth of dendrites are well inhibited due to the increase of the migration number, so that the non-dendrite deposition is facilitated, and the longer cycle life and the higher safety performance are shown.
Example 7
This example tested Li-LiFePO based on modified diaphragm and commercial Polypropylene diaphragm 4 Cycling and rate performance of the battery.
Lithium metal is used as negative electrode, liFePO 4 Adding 2% of LiNO by mass fraction to the positive electrode, 1M LiTFSIDME/DOL (volume ratio is 1:1) 3 Li-LiFePO was assembled separately as an electrolyte in an argon glove box using the modified separator and commercial Polypropylene separator of example 2 4 And a battery.
LiFePO 4 The preparation method of the positive electrode plate comprises the following steps: preparing slurry of lithium iron phosphate powder, carbon black, carbon nano fibers, polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone and N-methyl pyrrolidone in a mass ratio of 37.43:4.68:2.34:4.94:1.23:49.38. Subsequently, the slurry was planetary ball-milled for 2 hours to obtain a uniformly viscous liquid slurry, which was cast onto a PET carrier tape using a doctor blade. Then, the electrode film is quickly transferred into deionized water to be soaked for 2 hours, and the electrode film is taken out after the phase inversion process is completed. Finally, the electrode was transferred to an 80 ℃ oven for drying.
Will assemble the Li-LiFePO 4 The battery was charged and discharged under constant current, and the performance obtained by the test was as shown in fig. 7.
FIG. 7 is Li-LiFePO in example 7 4 And (3) multiplying power and cycle performance graphs obtained by the battery. The cell using the modified separator had 87mAh cm at 10C -2 Is (1c=160 mAh g) -1 ) Whereas commercial polypropylene separators are only 67mAh cm -2 Is a capacity (a) of (a). At high load LiFePO 4 In the case of using an improved diaphragmThe capacity retention of the cell at 1C after 1700 cycles was about 80% with significantly higher cycling stability than the cell (b) using a commercial polypropylene separator.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. A modified separator for a lithium metal battery, characterized by: the modified diaphragm is characterized in that a modified layer is arranged on the surface of the diaphragm, and the chemical general formula of inorganic nano ceramic powder for preparing the modified layer is A (+m) x B (+n) y O z Wherein: 0<x/y is equal to or less than 4, and z=0.5 (mx+ny); a is a transition metal element, and the valence state of the element is +m; b is a main group metal element, and the valence state of the element is +n.
2. The modified separator for lithium metal batteries according to claim 1, characterized in that: a is at least one of La, Y and Fe, and B is at least one of In, sn, sb and Bi.
3. The modified separator for lithium metal batteries according to claim 1, characterized in that: the thickness of the modified layer is 1-20 mu m.
4. The modified separator for lithium metal batteries according to claim 1, characterized in that: the modified layer can be subjected to conversion-alloying reaction with the lithium metal anode through simple physical contact or electrochemical process to form the multifunctional intermediate layer.
5. The modified separator for lithium metal batteries according to claim 4, wherein: the composition of the intermediate layer is transition metal oxide, alloy of lithium and B metal, and lithium oxide Li 2 O。
6. A method for producing the modified separator according to any one of claims 1 to 5, comprising the steps of:
step 1, synthesizing A x B y O z Precursor powder;
step 2, dispersing the precursor powder in a dispersing agent, and performing sanding treatment to obtain nano-sized finished product powder;
and step 3, uniformly mixing the finished powder with the high polymer solution, coating the mixture on the surface of the diaphragm, and drying to obtain the modified diaphragm.
7. The method of manufacturing according to claim 6, wherein: in the step 2, the dispersing agent is at least one of water, ethanol and acetone, and the mass fraction of the precursor powder dispersed in the dispersing agent is 5% -25%.
8. The method of manufacturing according to claim 6, wherein: in the step 2, the rotational speed of the sanding treatment is 2000-3000 r min -1 The sanding time is 20-120 min.
9. The method of manufacturing according to claim 6, wherein: in the step 3, the membrane is at least one of a polyethylene membrane, a polypropylene membrane, a polyethylene/polypropylene/polyethylene three-layer membrane, a glass cellulose membrane and a non-woven fabric membrane.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311750305.XA CN117638406A (en) | 2023-12-19 | 2023-12-19 | Modified diaphragm for lithium metal battery and preparation method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311750305.XA CN117638406A (en) | 2023-12-19 | 2023-12-19 | Modified diaphragm for lithium metal battery and preparation method thereof |
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| CN117638406A true CN117638406A (en) | 2024-03-01 |
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| CN202311750305.XA Pending CN117638406A (en) | 2023-12-19 | 2023-12-19 | Modified diaphragm for lithium metal battery and preparation method thereof |
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