CN115020916A - Lithium-sulfur battery diaphragm and preparation method and application thereof - Google Patents
Lithium-sulfur battery diaphragm and preparation method and application thereof Download PDFInfo
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- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 239000000463 material Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 20
- 238000012986 modification Methods 0.000 claims abstract description 19
- 230000004048 modification Effects 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 18
- 239000011230 binding agent Substances 0.000 claims abstract description 9
- 239000006258 conductive agent Substances 0.000 claims abstract description 9
- 239000004743 Polypropylene Substances 0.000 claims abstract description 4
- -1 polypropylene Polymers 0.000 claims abstract description 4
- 229920001155 polypropylene Polymers 0.000 claims abstract description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 35
- 229910052744 lithium Inorganic materials 0.000 claims description 35
- 229920000058 polyacrylate Polymers 0.000 claims description 24
- 238000010438 heat treatment Methods 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 13
- 239000000243 solution Substances 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- 150000002696 manganese Chemical class 0.000 claims description 7
- 239000012266 salt solution Substances 0.000 claims description 7
- 239000002002 slurry Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 239000002243 precursor Substances 0.000 claims description 6
- 239000002033 PVDF binder Substances 0.000 claims description 5
- 229920002125 Sokalan® Polymers 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- 238000004108 freeze drying Methods 0.000 claims description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- 150000002815 nickel Chemical class 0.000 claims description 5
- 239000004584 polyacrylic acid Substances 0.000 claims description 5
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 5
- 238000001354 calcination Methods 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 238000002425 crystallisation Methods 0.000 claims description 3
- 230000008025 crystallization Effects 0.000 claims description 3
- 238000001704 evaporation Methods 0.000 claims description 3
- 230000008020 evaporation Effects 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 3
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 238000003760 magnetic stirring Methods 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 abstract description 10
- 230000003647 oxidation Effects 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 9
- 230000009467 reduction Effects 0.000 abstract description 8
- 238000003487 electrochemical reaction Methods 0.000 abstract description 7
- 230000003197 catalytic effect Effects 0.000 abstract description 5
- 230000001351 cycling effect Effects 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 230000002457 bidirectional effect Effects 0.000 abstract description 4
- 238000007599 discharging Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 12
- 238000011056 performance test Methods 0.000 description 11
- 229920001021 polysulfide Polymers 0.000 description 10
- 239000005077 polysulfide Substances 0.000 description 9
- 150000008117 polysulfides Polymers 0.000 description 9
- 238000006722 reduction reaction Methods 0.000 description 9
- 239000003792 electrolyte Substances 0.000 description 7
- 238000004146 energy storage Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000012528 membrane Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 description 2
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical group O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 description 2
- 229960002635 potassium citrate Drugs 0.000 description 2
- 239000001508 potassium citrate Substances 0.000 description 2
- QEEAPRPFLLJWCF-UHFFFAOYSA-K potassium citrate (anhydrous) Chemical group [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 description 2
- 235000011082 potassium citrates Nutrition 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 229910018091 Li 2 S Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000012876 carrier material Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 description 1
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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- 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
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Abstract
The invention discloses a lithium-sulfur battery diaphragm and a preparation method and application thereof, and belongs to the technical field of lithium-sulfur batteries. The lithium-sulfur battery diaphragm comprises a diaphragm substrate and a modification layer coated on the surface of the diaphragm substrate; the diaphragm substrate is a polypropylene diaphragm,the modification layer comprises a conductive agent, a binder and a functional material. The lithium-sulfur battery diaphragm can catalyze the reduction of LiPS in the discharging process and can catalyze Li in the charging process 2 The oxidation of S has an oxidation/reduction bidirectional catalytic function, which is beneficial to improving the charge-discharge speed of the lithium-sulfur battery and increasing the charge-discharge capacity of the battery. At the same time, due to insulating Li at the interface 2 S is not accumulated, and the electrochemical reaction interface is effectively improved, so that the cycling stability of the lithium-sulfur battery is also improved.
Description
Technical Field
The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a lithium-sulfur battery diaphragm and a preparation method and application thereof.
Background
With the development of technology and industry, the demand for high specific energy storage devices is gradually increasing. The lithium-sulfur battery has wide application prospect by virtue of the advantages of high theoretical specific capacity, high theoretical energy density and low cost of sulfur.
Lithium-sulfur batteries undergo a complex series of electrochemical reactions during charging and discharging, involving a multi-electron participation and multi-reaction step solid-liquid-solid conversion reaction, in which lithium polysulfide (LipS) is reduced during discharging, and lithium sulfide (Li) is charged during charging 2 S) has poor reaction kinetics performance, which reduces the utilization rate of active substance sulfur and seriously influences the improvement of the energy storage performance of the lithium-sulfur battery.
Designing a sulfur anode carrier or introducing a membrane modification layer is a strategy for improving the practical operation energy storage capacity of the lithium-sulfur battery, which is proposed in the research and industrial circles at present. These carrier materials or modifier layer materials primarily promote the discharge process, including the reduction of lithium polysulfides, and Li 2 And (4) a uniform nucleation step of S. However, as a device capable of repeated charge/discharge, the electrochemical reaction kinetics of the battery are not sufficient to enhance the discharge process while neglecting the charge process. Moreover, the scheme of only enhancing the discharge process and neglecting the charge process can in turn seriously deteriorate the subsequent discharge process, since only after the discharge is enhanced, Li will inevitably result after many charge-discharge cycles 2 S accumulates continuously at the electrochemical reaction interface, while Li 2 S has the characteristic of obvious ion and electron double insulation, and the accumulation of S can further hinder the proceeding of electrochemical reaction (battery energy storage) in which electron ions need to participate, namely, the energy storage performance of the lithium-sulfur battery is limited to be prolonged in the real sense.
Disclosure of Invention
Aiming at the defects of the prior art in order to develop the energy storage technology of the lithium-sulfur battery, the invention provides a lithium-sulfur battery with oxidation/reductionA lithium-sulfur battery diaphragm with a bidirectional catalytic function, and a preparation method and application thereof. The prepared lithium-sulfur battery diaphragm can provide a large number of catalytic active sites, can effectively adsorb LiPS and promote lithium ions (Li) + ) The mass transfer capacity of (1). It can catalyze both the reduction of LipS during discharge and Li during charge 2 The oxidation of S has an oxidation/reduction bidirectional catalytic function, and is beneficial to improving the charge and discharge speed of the lithium-sulfur battery and increasing the charge and discharge capacity of the battery. At the same time, due to insulating Li at the interface 2 S is not accumulated, and the electrochemical reaction interface is effectively improved, so that the cycling stability of the lithium-sulfur battery is also improved.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a lithium-sulfur battery diaphragm, which comprises a diaphragm substrate and a modification layer coated on the surface of the diaphragm substrate; the diaphragm substrate is a polypropylene diaphragm (Celgard 2500), and the modification layer comprises a conductive agent, a binder and a functional material; the functional material is MnO x -NiO y C and/or lithium polyacrylate, x has a value in the range of 1<x<2, y is in the range of 0<y<1。
Further, the thickness of the diaphragm substrate is 20-30 μm, and the thickness of the modification layer is 10-15 μm; the conductive agent is conductive carbon black; the binder is polyvinylidene fluoride.
The lithium polyacrylate in the functional material of the invention enriches Li at the interface of the diaphragm and the sulfur anode + Substances which participate in the reaction, such as LiPS and electrons, provide sufficient reactants for the reciprocating charge/discharge process; MnO x -NiO y the/C being responsible for carrying out bidirectional catalysis of oxidation/reduction, i.e. MnO during discharge x Effectively adsorb LiPS and NiO y Significantly catalyze the reduction of LipS, MnO x And NiO y The adsorption-catalysis synergistic effect is exerted, and the discharge (reduction reaction) performance is jointly improved; during charging, MnO x And NiO y All catalyze Li 2 And the oxidation of S improves the charging (oxidation reaction) performance of the lithium-sulfur battery. The carbon material having a high specific surface area is a metal oxideDiffusion provides convenience and facilitates the exposure of more catalytically active sites of the metal oxide on the surface of the membrane. And the multiple technical schemes are combined, so that the energy storage performance of the lithium-sulfur battery is promoted.
The invention provides a preparation method of a lithium-sulfur battery diaphragm, which comprises the following steps:
MnO of x -NiO y Mixing the/C, the lithium polyacrylate, the conductive agent and the binder, grinding, adding N-methyl pyrrolidone to adjust viscosity, and enabling the slurry to have certain fluidity to obtain a modified layer slurry; and coating the modification layer slurry on the surface of a diaphragm substrate by using a 100-micron scraper, and drying to obtain the lithium-sulfur battery diaphragm.
Further, the MnO x -NiO y The preparation method of the/C comprises the following steps: dissolving a carbon source in water to obtain a carbon source solution, dissolving a manganese salt solution and a nickel salt in water to obtain a mixed solution, dropwise adding the mixed solution into the carbon source solution, and stirring and heating to obtain a precursor material; calcining the precursor material, washing and drying to obtain MnO x -NiO y /C。
Further, the carbon source is potassium citrate, the manganese salt solution is a manganese nitrate solution, and the nickel salt is nickel nitrate hexahydrate.
Further, the concentration of the manganese salt solution is 50 wt%; the mass ratio of the carbon source to the manganese salt solution to the nickel salt is 10-12: 0.6-1: 0.3-0.5; the stirring is magnetic stirring at normal temperature for 60 min; the heating is evaporation crystallization in a water bath at 80 ℃.
Further, the conditions of the calcination treatment are as follows: heating to 200 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 1h, continuing heating to 800 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 2h, then cooling to 500 ℃ at the cooling rate of 5 ℃/min, and finally cooling to room temperature along with the furnace; the washing is washing with deionized water; the drying is carried out in a vacuum drying oven at 60 ℃ for 6 h.
Further, the preparation method of the lithium polyacrylate comprises the following steps: and dissolving lithium hydroxide in water, adding polyacrylic acid, stirring, and freeze-drying to obtain the lithium polyacrylate.
Further, the mass volume ratio of the lithium hydroxide to the water to the polyacrylic acid is 0.3-0.5 g to 5mL to 1-3 g; the stirring is carried out for 24 hours at normal temperature; the freeze-drying time was 12 h.
Further, the MnO x -NiO y The mass ratio of the/C, the lithium polyacrylate, the conductive agent and the binder is 5-5.5: 0.5-1: 3: 1; the drying is carried out in a drying oven at 60 ℃ for 6 h.
The invention also provides an application of the lithium-sulfur battery diaphragm in the preparation of a lithium-sulfur battery.
The invention has the beneficial effects that:
(1) in the invention, MnO is added x -NiO y And the mixture of the/C and the lithium polyacrylate is used as a functional material coated on the surface of the diaphragm substrate. First using MnO x And NiO y The synergistic effect of the two components can effectively adsorb lithium polysulfide, catalyze the reduction of the lithium polysulfide and oxidize the lithium sulfide; the carbon material provides convenience for the dispersion of the metal oxide, is beneficial to the exposure of more active sites on the surface of the diaphragm, efficiently catalyzes the redox reaction of lithium polysulfide bidirectionally, improves the electrochemical reaction interface condition of the lithium-sulfur battery, and improves the cycle stability of the lithium-sulfur battery.
(2) In the invention, MnO is added x -NiO y and/C and lithium polyacrylate are coated on the surface of the diaphragm substrate. The introduction of the lithium polyacrylate improves the condition of poor hydrophilic characteristic between the surface of the polypropylene diaphragm matrix and the electrolyte; the wettability of the electrolyte to the diaphragm is enhanced, and the construction of more reaction interfaces and the improvement of ion mass transfer capacity are facilitated.
(3) In the invention, MnO is added x -NiO y and/C and lithium polyacrylate are coated on the surface of the diaphragm substrate. The introduction of the lithium polyacrylate can improve the ion diffusion capacity and cooperate with MnO x -NiO y the/C forms more reaction interfaces containing lithium polysulfide, lithium ions and electrons; this further promotes the kinetic properties of the membrane modification layer in catalyzing the conversion of lithium polysulfide. The rate capability and the cycle performance of the lithium-sulfur battery are also obviously improved even in a low electrolyte system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a photograph of a lithium sulfur battery separator of example 1;
FIG. 2 shows a lithium-sulfur battery assembled with example 3, comparative examples 1 to 2, and a separator having only a substrate (E/S ═ 23. mu.L. mg) -1 ) The electrochemical multiplying power performance test result of (2);
FIG. 3 shows a lithium sulfur battery assembled with the separator of example 1 (E/S-8. mu.L. mg) -1 ) The electrochemical cycle performance test result of (1).
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but rather as a more detailed description of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the documents are cited. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including but not limited to.
Example 1
The embodiment provides a lithium-sulfur battery diaphragm and a preparation method thereof:
(1) 10.381g of potassium citrate is weighed and placed in a beaker 1, 0.763g of manganese nitrate solution (50 wt%) and 0.310g of nickel nitrate hexahydrate are weighed and placed in a beaker 2, deionized water is respectively added to the solutions and completely dissolved, the solution in the beaker 2 is dripped into the beaker 1, the mixture is magnetically stirred for 60 minutes at normal temperature, and then the mixture is placed in a water bath kettle at 80 ℃ for evaporation and crystallization to obtain a precursor material.
(2) And (2) placing the precursor material in the step (1) in a high-temperature tube furnace, heating to 200 ℃ at a heating rate of 2 ℃/min, preserving heat for 1h, continuing heating to 800 ℃ at a heating rate of 2 ℃/min, preserving heat for 2h, continuing cooling to 500 ℃ at a cooling rate of 5 ℃/min, and then cooling to room temperature along with the tube furnace. Washing the calcined material with deionized water, and drying in a vacuum drying oven at 60 deg.C for 6h to obtain MnO x -NiO y a/C composite material.
(3) 0.359g of lithium hydroxide is weighed and completely dissolved in 5mL of deionized water, 2g of polyacrylic acid (molecular weight of 2000) is continuously added, stirring is carried out for 24h at normal temperature, and then the solid product lithium polyacrylate is obtained after freeze drying is carried out for 12 h.
(4) MnO obtained in the step (2) x -NiO y C, the mass ratio of the lithium polyacrylate obtained in the step (3), the conductive carbon black and the PVDF is 5.5:0.5:3:1And (3) mixing, placing in an agate mortar, grinding until the particles are fine and uniformly dispersed, transferring to a beaker, adding N-methyl pyrrolidone to adjust the viscosity, so that the obtained slurry has certain fluidity, coating the surface of a diaphragm matrix with the obtained slurry by using a 100-micrometer scraper, drying for 6 hours in a drying oven at 60 ℃ to obtain the lithium-sulfur battery diaphragm, wherein a physical photograph is shown in figure 1. The diameter of the diaphragm obtained by slicing is 18mm, the thickness of the obtained diaphragm substrate is 25 mu m, and the thickness of the modified layer is 12 mu m
Example 2
This example provides a lithium sulfur battery separator and method of making the same, except for MnO x -NiO y The example was repeated except that the components (C)/C, lithium polyacrylate, conductive carbon black and PVDF were mixed in a mass ratio of 5:1:3:1, and the balance was the same as in example 1.
Example 3
This example provides a lithium-sulfur battery separator and a method for preparing the same, and the difference from example 1 is that the functional material of the separator modification layer of the lithium-sulfur battery is only MnO x -NiO y /C。
Comparative example 1
This comparative example provides a separator for a lithium-sulfur battery and a method for preparing the same, and is different from example 3 in that the functional material of the separator modification layer of the lithium-sulfur battery is only MnO x /C。
Comparative example 2
The comparative example provides a lithium-sulfur battery separator and a preparation method thereof, and the difference from example 3 is that the functional material of the lithium-sulfur battery separator modification layer is NiO only y /C。
Assembling the battery:
the lithium sulfur battery separators of each example and comparative example were assembled into a button cell in a glove box. The specific method comprises the following steps: mixing elemental sulfur, conductive carbon black and polyvinylidene fluoride according to a mass ratio of 6: 3:1, preparing a positive plate by coating after size mixing, and assembling the lithium-sulfur battery by taking the lithium plate as a negative plate, the lithium-sulfur battery diaphragm prepared in each embodiment and comparative example as a diaphragm and a lithium bis (trifluoromethanesulfonyl) imide solution (DOL and DME as solvents) as electrolyte, wherein a modification layer of the lithium-sulfur battery diaphragm faces to the positive electrode.
A Land CT-2001A type electrochemical test system is adopted to test the rate capability and the cycle performance of the lithium-sulfur battery, and the test voltage interval is 1.7-2.8V. The range of current density in the rate performance test is 0.2C-5C, and specifically 0.2C, 0.5C, 1C, 2C, 3C, 4C and 5C respectively; the current density in the cycle performance test was 0.5C and 1C, respectively.
Lithium sulfur battery assembled using the separator of example 1 when E/S is 8 μ L mg -1 When the alloy is circulated for 350 circles under the current density of 0.5C, 564 mAh.g can be realized -1 Specific discharge capacity of (a); when E/S is 12 mu L.mg -1 When the current density is respectively 4C and 5C, the reversible specific capacity respectively reaches 562 and 487 mAh.g -1 。
Table 1 shows specific discharge capacity results obtained from electrochemical cycling performance tests of the lithium-sulfur battery assembled with the separator of each example and comparative example. Table 2 shows the reversible specific capacity results obtained from electrochemical rate performance tests of the lithium-sulfur battery assembled with the separator of each example.
TABLE 1
TABLE 2
Lithium sulfur batteries assembled from the separators of example 3, comparative example 1, and comparative example 2 (E/S23 μ L · mg) -1 ) Comparing the test results of the cycle performance, the MnO can be known x -NiO y the/C can effectively improve the discharge specific capacity and the cycling stability of the lithium-sulfur battery due to the fact that the/C can efficiently and bidirectionally catalyze the oxidation/reduction reaction of lithium polysulfide; MnO x And NiO y The two can well play a synergistic catalytic role, and one is not necessary.
Through the separators of example 1 and example 3Assembled lithium sulfur battery (E/S-12. mu.L. mg) -1 ) The cycle performance test result is compared with the rate performance test result, and the specific discharge capacity of the lithium-sulfur battery under low electrolyte can be further improved by introducing the lithium polyacrylate, and particularly, the improvement effect is more obvious under high current density. This is attributed to the fact that on the one hand, the introduction of lithium polyacrylate can improve the mass transfer capacity of lithium ions; on the other hand, lithium polyacrylate in combination with MnO x -NiO y the/C creates more reactive interfaces containing lithium polysulphides, lithium ions and electrons.
Lithium sulfur battery assembled by the separators of example 1 and example 2 (E/S ═ 12 μ L · mg -1 ) The cycle performance test result is compared with the rate performance test result, and the introduction of a proper amount of lithium polyacrylate can improve the electrochemical performance of the lithium-sulfur battery; and the introduction of excessive lithium polyacrylate has the effect of being counterproductive. More reactive interfaces are constructed in the diaphragm modification layer in the embodiment 1, so that the discharge specific capacity of the low-electrolyte lithium-sulfur battery is remarkably improved, and the high-rate display is more remarkable.
Fig. 2-3 are results of electrochemical rate performance and cycle performance tests of the lithium sulfur battery assembled with the separators of examples 1-3 and comparative examples 1-2 at different E/S. It can be seen from fig. 2 that the lithium sulfur battery assembled using the separator of example 3 has more excellent rate performance than comparative examples 1 and 2 due to MnO x -NiO y the/C can efficiently catalyze the oxidation/reduction reaction of lithium polysulfide bidirectionally. As can be seen from fig. 3, the lithium-sulfur battery assembled using the separator of example 1 was operated in a lean electrolyte system (E/S ═ 8 μ L · mg -1 ) Still can show excellent cycling stability, and can be seen that the multifunctional lithium-sulfur battery diaphragm has wide application prospect.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (10)
1. The lithium-sulfur battery diaphragm is characterized by comprising a diaphragm substrate and a modification layer coated on the surface of the diaphragm substrate; the diaphragm substrate is a polypropylene diaphragm, and the modification layer comprises a conductive agent, a binder and a functional material; the functional material is MnO x -NiO y C and/or lithium polyacrylate, x has a value in the range of 1<x<2, y is in the range of 0<y<1。
2. The lithium-sulfur battery separator according to claim 1, wherein the thickness of the separator substrate is 20 to 30 μm, and the thickness of the modification layer is 10 to 15 μm; the conductive agent is conductive carbon black; the binder is polyvinylidene fluoride.
3. A method of preparing the lithium-sulfur battery separator according to claim 1 or 2, comprising the steps of:
MnO of x -NiO y Mixing the/C, the lithium polyacrylate, the conductive agent and the binder, grinding, and adding N-methyl pyrrolidone to adjust viscosity to obtain modified layer slurry; and coating the modification layer slurry on the surface of a diaphragm substrate, and drying to obtain the lithium-sulfur battery diaphragm.
4. The method of claim 3, wherein the MnO is x -NiO y The preparation method of the/C comprises the following steps: dissolving a carbon source in water to obtain a carbon source solution, dissolving a manganese salt solution and a nickel salt in water to obtain a mixed solution, dropwise adding the mixed solution into the carbon source solution, and stirring and heating to obtain a precursor material; calcining the precursor material, washing and drying to obtain MnO x -NiO y /C。
5. The method according to claim 4, wherein the concentration of the manganese salt solution is 50 wt%; the mass ratio of the carbon source to the manganese salt solution to the nickel salt is 10-12: 0.6-1: 0.3-0.5; the stirring is magnetic stirring at normal temperature for 60 min; the heating is evaporation crystallization in a water bath at 80 ℃.
6. The method according to claim 4, wherein the calcination treatment is carried out under the following conditions: heating to 200 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 1h, continuing heating to 800 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 2h, then cooling to 500 ℃ at the cooling rate of 5 ℃/min, and finally cooling to room temperature along with the furnace; the washing is washing with deionized water; the drying is carried out in a vacuum drying oven at 60 ℃ for 6 h.
7. The preparation method according to claim 3, wherein the preparation method of the lithium polyacrylate comprises the following steps: and dissolving lithium hydroxide in water, adding polyacrylic acid, stirring, and freeze-drying to obtain the lithium polyacrylate.
8. The preparation method according to claim 7, wherein the mass-to-volume ratio of the lithium hydroxide, the water and the polyacrylic acid is 0.3-0.5 g:5mL: 1-3 g; the stirring is carried out for 24 hours at normal temperature; the freeze-drying time was 12 h.
9. The method of claim 3, wherein the MnO is x -NiO y The mass ratio of the/C, the lithium polyacrylate, the conductive agent and the binder is 5-5.5: 0.5-1: 3: 1; the drying is carried out in a drying oven at 60 ℃ for 6 h.
10. Use of a lithium-sulfur battery separator according to claim 1 or 2 in the preparation of a lithium-sulfur battery.
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