CN112072169B - All-solid-state electrolyte, composition thereof, electrode and all-solid-state lithium ion battery - Google Patents

All-solid-state electrolyte, composition thereof, electrode and all-solid-state lithium ion battery Download PDF

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CN112072169B
CN112072169B CN201910496660.6A CN201910496660A CN112072169B CN 112072169 B CN112072169 B CN 112072169B CN 201910496660 A CN201910496660 A CN 201910496660A CN 112072169 B CN112072169 B CN 112072169B
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perfluoropolyether
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composition
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CN112072169A (en
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刘荣华
高磊
李婷婷
吴金祥
单军
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Huizhou BYD Industrial Co Ltd
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/137—Electrodes based on electro-active polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to the field of all-solid-state lithium ion batteries, in particular to an all-solid-state electrolyte, a composition and an electrode thereof, and an all-solid-state lithium ion battery. The all-solid-state electrolyte composition contains PVDF-HFP, perfluoropolyether and a first lithium salt; the fluorine content of the perfluoropolyether is 40 to 90 wt%. The all-solid-state electrolyte provided by the invention has higher ionic conductivity and mechanical strength, and the obtained all-solid-state lithium ion battery has excellent high battery cycle performance and specific capacity.

Description

All-solid-state electrolyte, composition thereof, electrode and all-solid-state lithium ion battery
Technical Field
The invention relates to the field of all-solid-state lithium ion batteries, in particular to an all-solid-state electrolyte, a composition and an electrode thereof, and an all-solid-state lithium ion battery.
Background
At present, liquid electrolyte is mostly used as a conductive substance in lithium ion batteries on the market, but in the using process, the liquid electrolyte is volatile, flammable and explosive, so that a plurality of safety problems are caused; and it is prone to develop lithium dendrites, limiting the use of metallic lithium as a negative electrode in batteries. Therefore, Solid Polymer Electrolytes (SPE) have been proposed to replace liquid electrolytes. The solid polymer electrolyte membrane not only functions as ion conduction, but also prevents contact between the positive and negative electrodes. And because of its strong plasticity, can make into the film of different shapes according to different demands, the pliability is good, can bear the pressure of electrode in the charge-discharge process, and high temperature stability is good, has greatly improved the security of lithium cell.
CN101183727A relates to an all-solid-state electrolyte and a preparation method and application thereof. The invention discloses an all-solid-state electrolyte which is composed of lithium salt, polyethylene oxide (PEO) and ultrafine powder filler. The provided all-solid-state electrolyte is matched with a metallic lithium cathode and does not existThe potential safety hazard of liquid electrolyte leakage, excellent mechanical property and easy molding. However, the electrolyte provided by the invention has lower ionic conductivity (the ionic conductivity at room temperature is 10)-6-10-7S/cm order of magnitude), poor mechanical strength, reduced strength at high temperature, application to batteries, influence on the exertion of battery capacity, and poor battery cycle stability. The reason for the above disadvantages is that the PEO system polymer electrolyte has the following disadvantages:
1) PEO has a low glass transition temperature and is soft at room temperature.
2) In the electrolyte, lithium ions and oxygen atoms in PEO are continuously complexed and dissociated through coordination, so that the lithium ions are transferred, and Li+The transport rate in the crystalline region is 2-3 orders of magnitude lower than in the amorphous region. PEO has a higher crystallinity, so the room temperature conductivity of pure PEO-lithium salt systems is generally lower (10)-6-10-7S/cm) is difficult to meet the requirements of practical application.
Disclosure of Invention
The invention aims to provide an all-solid-state electrolyte with high ionic conductivity and high mechanical strength, a composition thereof and an all-solid-state lithium ion battery, wherein the obtained all-solid-state lithium ion battery has high cycle performance and specific capacity.
In order to accomplish the above object, an aspect of the present invention provides an all-solid electrolyte composition comprising PVDF-HFP, perfluoropolyether, and a first lithium salt; the content of fluorine in the perfluoropolyether is 40 to 90 wt%.
In a second aspect, the present invention provides an all-solid electrolyte comprising or produced from the above composition.
In a third aspect, the invention provides an electrode comprising the above composition.
A fourth aspect of the invention provides an all-solid lithium ion battery including the above-described all-solid electrolyte and the above-described electrode.
The all-solid-state electrolyte provided by the invention has higher ionic conductivity and mechanical strength, wherein the ionic conductivity at room temperature can reach 1 x 10-5～8×10-4S/cm, the mechanical strength can reach 3-10 MPa; what is needed isThe obtained all-solid-state lithium ion battery has excellent specific capacity and battery cycle performance.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In one aspect, the present invention provides an all-solid-state electrolyte composition comprising PVDF-HFP, perfluoropolyether, and a first lithium salt; the fluorine content of the perfluoropolyether is 40 to 90 wt%.
According to the invention, the ionic conductivity of the obtained all-solid-state electrolyte can be improved by adopting the perfluoropolyether with the fluorine content of 40-90 wt%, and the main reasons are as follows: the perfluoropolyether with the fluorine content of 40-90 wt% interacts with fluorine in the PVDF-HFP, so that the interaction of the PVDF-HFP and the lithium salt is weakened, and the dissociation degree of the lithium salt is greatly improved; the interaction of the perfluoropolyether and lithium salt anions weakens the action of the anions and lithium ions; perfluoropolyether can reduce the crystallinity of PVDF-HFP, thereby facilitating lithium ion conduction. Controlling the fluorine content to be 40-90 wt%, which can give consideration to high ionic conductivity and mechanical strength, and if the fluorine content ratio is too low, the ionic conductivity is not obviously improved; if the fluorine content is too high, the strength of the electrolyte membrane is significantly reduced. In order to better match the PVDF-HFP, the perfluoropolyether, and the first lithium salt in the composition, preferably, the perfluoropolyether is contained in an amount of 5 to 600 parts by weight and the first lithium salt is contained in an amount of 20 to 100 parts by weight, relative to 100 parts by weight of PVDF-HFP. More preferably, the perfluoropolyether is contained in an amount of 10 to 400 parts by weight and the first lithium salt is contained in an amount of 30 to 80 parts by weight, relative to 100 parts by weight of PVDF-HFP. Still more preferably, the perfluoropolyether is contained in an amount of 30 to 200 parts by weight and the first lithium salt is contained in an amount of 40 to 60 parts by weight, relative to 100 parts by weight of PVDF-HFP.
According to the invention, the perfluoropolyether has a main chain with ether structural units and the C of the main chain is substantially fully substituted by fluorine. Wherein the ether structural unit on the main chain of the perfluoropolyether can be one or more of the following structural units:
and (3) type K:
Figure BDA0002088833080000031
type D:
Figure BDA0002088833080000032
and (2) Z type:
Figure BDA0002088833080000033
y type:
Figure BDA0002088833080000034
according to the present invention, in order to obtain higher ionic conductivity and mechanical strength of the obtained electrolyte membrane, the fluorine content in the perfluoropolyether is preferably 50 to 80 wt%.
According to the present invention, in order to make the perfluoropolyether better suitable for use in the composition of the present invention, it is preferred that the perfluoropolyether has a molecular weight of 100 to 10,000g/mol, preferably 1,000 to 5,000 g/mol.
Wherein the perfluoropolyether can be non-functionalized perfluoropolyether, preferably functionalized perfluoropolyether. Wherein the functionalization is selected from silane coupling agents, preferably one or more functional modifications of silane coupling agents with alcoholic hydroxyl groups and silane coupling agents with carbon-carbon double bonds, such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltriethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylethyldiethoxysilane, N-acryloyloxy-propylmethyldimethoxysilane, N-acryloyloxypropyltrimethoxysilane, N-acryloyloxyethyltrimethoxysilane, N-acryloyloxypropyltrimethoxysilane, N-acryloyloxypropyltriethoxysilane, N-acryloyloxyethyltrimethoxysilane, N-acryloyloxypropyltrimethoxysilane, N-propyltrimethoxysilane, N-acryloyloxyethyltrimethoxysilane, N-propyltrimethoxysilane, N-methoxysilane, N-propyltrimethoxysilane, N-methoxysilane, N-propylsilane, N-methoxysilane, N-hydroxysilane, N-hydroxysilylether-ethyldiethoxy-functional modification of the group, 3-methacryloxypropylethyldiethoxysilane, 3-acryloxypropyldimethylethoxysilane, 3-methacryloxypropyldimethylethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane and allyltriethoxysilane. Functionalization of the perfluoropolyether can be accomplished by methods conventional in the art, for example, the end groups of the perfluoropolyether can be made to have functionalized end groups, the perfluoropolyether can be made to have pendant functionalized groups as described above, and the like. The functionalized perfluoropolyether can be coupled, polymerized or crosslinked with other polymer components in the all-solid-state electrolyte composition, thereby being beneficial to increasing the mechanical strength of the electrolyte membrane and improving the ionic conductivity.
The PVDF-HFP is a common polymer component of the all-solid-state electrolyte, and is optimized according to the invention, and preferably has a molecular weight of 10,000-1,000,000 g/mol, preferably 100,000-800,000 g/mol. Preferably, in the PVDF-HFP, the content of a structural unit provided by vinylidene fluoride is 75-90 mol%, and the content of a structural unit provided by hexafluoropropylene is 10-25 mol%. When the PVDF-HFP with the optimized structure is adopted, the regularity of a chain segment can be damaged after the PVDF and a proper amount of hexafluoropropylene are copolymerized, the crystallinity of the obtained PVDF-HFP copolymer is reduced, the ionic conductivity is further improved, the flexibility of the chain segment is increased, and the all-solid-state polymer electrolyte membrane with higher ionic conductivity and mechanical strength can be formed more favorably.
According to the present invention, the first lithium salt is one or more of lithium salts for all-solid-state electrolytes, preferably LiN (CF)3SO2)2、LiClO4、LiBF4、LiPF6、LiCF3SO3And LiN (CF)3SO2)3One or more of (a).
In a second aspect, the present invention provides an all-solid-state electrolyte comprising or produced from the above composition.
The all-solid-state electrolyte provided by the invention can be only an all-solid-state electrolyte containing the composition, or can be an all-solid-state electrolyte prepared from the composition by a certain preparation method.
Wherein, the preparation method of the all-solid-state electrolyte preferably comprises the following steps:
and (2) mixing the PVDF-HFP and a first lithium salt in an organic solvent (for example, magnetically stirring at 15-30 ℃ for 10-36 hours), introducing the perfluoropolyether, mixing (for example, magnetically stirring at 15-30 ℃ for 10-60 minutes), and removing the solvent (for example, heating at 50-90 ℃ to dry to form a film), thus obtaining the all-solid-state electrolyte.
Wherein the organic solvent may be selected from one or more of N-methylpyrrolidone (NMP), N-Dimethylformamide (DMF), Dimethylsulfoxide (DMSO), benzene, carbon tetrachloride, chloroform, toluene, xylene, etc., and may be used in a wide range, for example, 200 to 400 parts by weight with respect to 100 parts by weight of PVDF-HFP.
The all-solid-state electrolyte obtained by the invention has higher ionic conductivity, lower crystallinity and proper flexibility. In particular, the ion conductivity of the all-solid electrolyte can reach 1 x 10-5～8×10-4S/cm, the glass transition temperature is-10 to-50 ℃, and the stress-strain result is 3 to 10 MPa.
In a third aspect, the invention provides an electrode comprising the above composition.
The electrode may be a positive electrode or a negative electrode, and is preferably a positive electrode.
According to the present invention, the positive electrode includes a positive electrode current collector and a positive electrode material layer, and the composition is contained in the positive electrode material layer.
The positive current collector can adopt various current collectors used for lithium ion batteries in the prior art, such as copper foil, aluminum foil and the like.
The positive electrode material layer is mainly formed by positive electrode slurry containing a positive electrode active material, the all-solid-state electrolyte composition and a conductive agent. Wherein the positive electrode active material may beThe positive active material conventionally used in the art, for example, includes but is not limited to LiFePO4、LiCOO2、LiMnO2、LiMn2O4、LiNiO2、LiNixCoyMnzO2、LiNixCoyAlzO2And the like, wherein x + y + z is 1, 0. ltoreq. x.ltoreq.1, 0. ltoreq. y.ltoreq.1, and 0. ltoreq. z.ltoreq.1. The conductive agent may be a conductive agent conventionally used in the art, for example, the conductive agent includes one or more of acetylene black, superconducting carbon, conductive carbon black, conductive graphite, graphene, carbon nanotubes, carbon nanofibers, and the like.
Wherein, preferably, the weight ratio of the positive electrode active material, the all-solid-state electrolyte composition and the conductive agent is 60-80: 15-30: 1-10, preferably 70-75: 20-25: 1 to 5.
The dispersant used in the positive electrode slurry may be, for example, one or more of ethanol, isopropanol, butanol, pentanol, hexane, cyclohexane, ethyl acetate, and/or a mixture of these compounds, and the like. The amount of the dispersant may vary within a wide range, and for example, may be 0.5 to 5 parts by weight, relative to 100 parts by weight of the total weight of the positive electrode active material, the above-described all-solid electrolyte composition, and the conductive agent.
And coating the positive slurry on a positive current collector, and drying to obtain the positive electrode.
A fourth aspect of the invention provides an all-solid lithium ion battery including the above-described all-solid electrolyte and an electrode.
The lithium ion battery may be an all solid state lithium ion battery of conventional construction in the art, so long as it includes the all solid state electrolyte and electrodes of the present invention, preferably including the all solid state electrolyte and positive electrode described above.
Among them, when the cathode containing the all-solid electrolyte composition described above is employed, the cathode of the lithium ion battery may be various cathodes known in the art. The negative electrode may be made of lithium metal.
The present invention will be described in detail below by way of examples.
In the following examples:
the polymer PVDF-HFP-1 is PVDF-HFP available from Arkema, wherein the molecular weight of the polymer is 700,000g/mol, the content of structural units provided by vinylidene fluoride is 75 mol% and the content of structural units provided by hexafluoropropylene is 25 mol%.
The polymer PVDF-HFP-2 is PVDF-HFP available from Arkema, wherein the molecular weight of the polymer is 600,000g/mol, the content of structural units provided by vinylidene fluoride is 75 mol% and the content of structural units provided by hexafluoropropylene is 25 mol%.
The polymer PVDF-HFP-3 is PVDF-HFP available from Arkema, wherein the molecular weight of the polymer is 50,000g/mol, the content of structural units provided by vinylidene fluoride is 75 mol%, and the content of structural units provided by hexafluoropropylene is 25 mol%.
The polymer PVDF-HFP-4 is PVDF-HFP available from Arkema, wherein the molecular weight of the polymer is 1,000,000g/mol, the content of structural units provided by vinylidene fluoride is 75 mol% and the content of structural units provided by hexafluoropropylene is 25 mol%.
Perfluoropolyether # 1 was a non-functionalized perfluoropolyether available from aladdin, where the polymer had a molecular weight of 1,000g/mol and a fluorine content of 70 wt%.
Perfluoropolyether # 2 was a non-functionalized perfluoropolyether available from aladdin, where the polymer had a molecular weight of 2,000g/mol and a fluorine content of 70 wt%.
Perfluoropolyether # 3 was a non-functionalized perfluoropolyether available from aladdin, where the polymer had a molecular weight of 4,000g/mol and a fluorine content of 70 wt%.
Perfluoropolyether # 4 was a non-functionalized perfluoropolyether available from aladdin, where the polymer had a molecular weight of 100g/mol and a fluorine content of 70 wt%.
Perfluoropolyether # 5 was a non-functionalized perfluoropolyether available from aladdin, where the polymer had a molecular weight of 10,000g/mol and a fluorine content of 70 wt%.
Perfluoropolyether # 6 was a 3-aminopropyltriethoxysilane functionalized modified perfluoropolyether available from aladdin, where the molecular weight of the polymer was 3,000g/mol and the fluorine content was 70 wt%.
Perfluoropolyether # 7 was a 3-aminopropyltriethoxysilane functionalized modified perfluoropolyether available from aladdin, where the molecular weight of the polymer was 10,000g/mol and the fluorine content was 70 wt%.
PEO: product commercially available from Aladdin Industrial Co., weight average molecular weight 1,000 g/mol.
Example 1
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
Preparing an all-solid electrolyte:
(1) to 300 parts by weight of N-methylpyrrolidone (NMP) were added 100 parts by weight of polymer PVDF-HFP-1 and 55 parts by weight of LiN (CF)3SO2)2Magnetically stirring at room temperature (about 25 ℃) for 24 hours, and uniformly mixing;
(2) adding 80 parts by weight of perfluoropolyether No. 1 into the mixed material, and continuously magnetically stirring at room temperature (about 25 ℃) for 25min to uniformly mix to obtain electrolyte slurry;
(3) the resulting electrolyte slurry was dried at 60 ℃ to form a film, and cut into 19mm round pieces having a thickness of 80 μm, which was designated as an all-solid electrolyte membrane S1.
Preparation of the positive electrode:
(1) respectively mixing the anode active materials LiFePO4The electrolyte slurry obtained by the above method (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent acetylene black are uniformly dispersed in a dispersant ethanol (the amount of the dispersant is 200 parts by weight relative to 100 parts by weight of the total amount of the cathode active material, the electrolyte slurry (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent) according to a weight ratio of 70:25:5 to obtain a cathode slurry;
(2) the positive electrode slurry was uniformly coated on an aluminum foil by a coater, then dried at 60 ℃, and cut into a 13mm diameter circular sheet by a slicer, which was designated as positive electrode sheet a1, wherein the thickness of one side of the positive electrode material layer was about 30 μm.
Preparing a battery:
the positive electrode sheet a1, the all-solid electrolyte membrane S1, and the negative electrode lithium sheet were put into a glove box containing a high purity Ar atmosphere to prepare a button cell, designated as B1.
Example 2
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
Preparing an all-solid electrolyte:
(1) to 250 parts by weight of NMP were added 100 parts by weight of the polymer PVDF-HFP-2 and 50 parts by weight of LiN (CF)3SO2)2Magnetically stirring at room temperature (about 25 ℃) for 24 hours, and uniformly mixing;
(2) adding 50 parts by weight of perfluoropolyether 2#, and continuously magnetically stirring at room temperature (about 25 ℃) for 35min to uniformly mix to obtain electrolyte slurry;
(3) the resulting electrolyte slurry was dried at 70 ℃ to form a film, and cut into 19mm round pieces having a thickness of 80 μm, which was designated as an all-solid electrolyte membrane S2.
Preparation of the positive electrode:
(1) respectively mixing the anode active materials LiFePO4The electrolyte slurry obtained by the above method (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent acetylene black are uniformly dispersed in a dispersant ethanol (the amount of the dispersant is 200 parts by weight relative to 100 parts by weight of the total amount of the cathode active material, the electrolyte slurry (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent) according to a weight ratio of 70:25:5 to obtain a cathode slurry;
(2) the positive electrode slurry was uniformly coated on an aluminum foil by a coater, then dried at 60 ℃, and cut into a 13 mm-diameter circular sheet by a slicer, which was designated as positive electrode sheet a2, wherein the thickness of one side of the positive electrode material layer was about 30 μm.
Preparing a battery:
the positive electrode sheet a2, the all-solid electrolyte membrane S2, and the negative electrode lithium sheet were put into a glove box containing a high purity Ar atmosphere to prepare a button cell, designated as B2.
Example 3
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
Preparing an all-solid electrolyte:
(1) 100 parts by weight of PVDF-HFP-1 polymer and 40 parts by weight of LiN (CF) were added to 300 parts by weight of N-methylpyrrolidone (NMP)3SO2)2Magnetically stirring at room temperature (about 25 ℃) for 24 hours, and uniformly mixing;
(2) adding 30 parts by weight of perfluoropolyether No. 3 into the mixed material, and continuously magnetically stirring for 45min at room temperature (about 25 ℃) to uniformly mix to obtain electrolyte slurry;
(3) the resulting electrolyte slurry was dried at 80 ℃ to form a film, and cut into 19mm round pieces having a thickness of 80 μm, which was designated as an all-solid electrolyte membrane S3.
Preparation of the positive electrode:
(1) respectively mixing the anode active materials LiFePO4The electrolyte slurry obtained by the above method (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent acetylene black are uniformly dispersed in a dispersant ethanol (the amount of the dispersant is 200 parts by weight relative to 100 parts by weight of the total amount of the cathode active material, the electrolyte slurry (the amount is calculated as the residual amount after the solvent is removed) and the conductive agent) according to a weight ratio of 70:25:5 to obtain a cathode slurry;
(2) the positive electrode slurry was uniformly coated on an aluminum foil by a coater, then dried at 60 ℃, and cut into a 13 mm-diameter circular sheet by a slicer, which was designated as positive electrode sheet a3, wherein the thickness of one side of the positive electrode material layer was about 30 μm.
Preparing a battery:
the positive electrode sheet a3, the all-solid electrolyte membrane S3, and the negative electrode lithium sheet were put into a glove box containing a high purity Ar atmosphere to prepare a button cell, designated as B3.
Example 4
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
According to the method described in example 1, except that in the preparation of the all-solid electrolyte, LiN (CF)3SO2)2Amount of (A) to be usedPerfluoropolyether # 1 was used in an amount of 69 parts by weight for 11 parts by weight, to finally obtain all-solid electrolyte membrane S4, positive electrode sheet a4, and battery B4.
Example 5
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
According to the method described in example 1, except that in the preparation of the all-solid electrolyte, LiN (CF)3SO2)2Was used in an amount of 50 parts by weight, and perfluoropolyether # 1 was used in an amount of 7 parts by weight, to finally obtain an all-solid electrolyte membrane S5, a positive electrode sheet a5, and a battery B5.
Example 6
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
According to the method described in example 1, except that in the preparation of the all-solid electrolyte, LiN (CF)3SO2)2Was used in an amount of 10 parts by weight, and perfluoropolyether # 1 was used in an amount of 5 parts by weight, to finally obtain an all-solid electrolyte membrane S6, a positive electrode sheet a6, and a battery B6.
Examples 7 to 12
This example serves to illustrate the all-solid-state electrolyte, positive electrode and battery of the present invention.
The method of embodiment 1, except that:
in example 7: the perfluoropolyether No. 4 with equal weight parts is adopted to replace the perfluoropolyether No. 1, so that the all-solid electrolyte membrane S7, the positive plate A7 and the battery B7 are finally prepared;
in example 8: the perfluoropolyether No. 5 with equal weight parts is adopted to replace the perfluoropolyether No. 1, so that the all-solid electrolyte membrane S8, the positive plate A8 and the battery B8 are finally prepared;
in example 9: the perfluoropolyether No. 6 with equal weight parts is adopted to replace the perfluoropolyether No. 1, so that the all-solid electrolyte membrane S9, the positive plate A9 and the battery B9 are finally prepared;
in example 10: the perfluoropolyether No. 7 with equal weight parts is adopted to replace the perfluoropolyether No. 1, so that the all-solid electrolyte membrane S10, the positive plate A10 and the battery B10 are finally prepared;
in example 11: the PVDF-HFP-3 polymer with equal weight parts is adopted to replace the PVDF-HFP-1 polymer, so that the all-solid electrolyte membrane S11, the positive plate A11 and the battery B11 are finally prepared;
in example 12: the polymer PVDF-HFP-1 was replaced with equal parts by weight of the polymer PVDF-HFP-4, thereby finally producing the all-solid electrolyte membrane S12, the positive electrode sheet a12, and the battery B12.
Comparative example 1
According to the method described in example 1, except that perfluoropolyether # 1 was replaced with equal parts by weight of PEG, an all-solid electrolyte membrane DS1, a positive electrode sheet DA1, and a battery DB1 were finally prepared.
Comparative example 2
According to the method described in example 1, except that the polymer PVDF-HFP-1 was replaced with equal parts by weight of PEG, an all-solid electrolyte membrane DS2, a positive electrode sheet DA2, and a battery DB2 were finally prepared.
Test example 1
The mechanical properties of the sample are tested by using a universal tester (WDW-0.5, Shenzhen Junrui tester Co., Ltd.), the all-solid electrolyte membrane sample obtained in the above example is punched into a shape required by the test by using a mold in advance, the thickness of the sample is measured, and the sample is kept dry before the test. The tensile strength and puncture strength of the samples were measured using the respective molds, and the results are shown in Table 1.
TABLE 1
Figure BDA0002088833080000121
Figure BDA0002088833080000131
As can be seen from the table 1, the all-solid electrolyte membrane has excellent mechanical properties, the all-solid electrolyte membrane obtained by the optimized composition has excellent comprehensive mechanical properties, the tensile strength can reach 6.5-8.8 MPa, and the elongation at break can reach 70% -80%.
Test example 2
All solidThe ionic conductivity of the electrolyte membrane samples was measured by ac impedance and using a button cell at a temperature range of 30-80 ℃. Using a stainless steel sheet/electrolyte membrane/stainless steel sheet structure in a glove box (O)2<1ppm,H2O<1ppm) was prepared. Impedance test frequency range 105-0.5Hz and an amplitude of 5 mV. Before the impedance test, the sample is kept at the preset temperature for 60min, and the test results are shown in table 2.
TABLE 2
Figure BDA0002088833080000132
Figure BDA0002088833080000141
As can be seen from table 2, the all-solid electrolyte membrane of the present invention has a higher ionic conductivity, and the ionic conductivity of the resulting all-solid electrolyte membrane is higher in the preferred composition.
Test example 3
Taking about 10mg of all-solid electrolyte membrane sample, filling the sample with a crucible, preparing a DSC sample, and adding N2DSC test is carried out under the atmosphere, the temperature rising rate is 10 ℃/min, and the glass transition temperature obtained by the test is shown in Table 3.
TABLE 3
Figure BDA0002088833080000142
As can be seen from table 3, the all-solid electrolyte membrane of the present invention has a reduced glass transition temperature, melting point, and crystallinity, as compared to the comparative examples.
Test example 4
The battery performances of the batteries B1-B12 and DB1-DB2 obtained in the above example are tested, the obtained first discharge specific capacity and the discharge specific capacity after 20 cycles are shown in Table 4, and the specific test procedures are as follows.
The test process of the first discharge specific capacity comprises the following steps: the battery is placed in a thermostat at 45 ℃, the charging and discharging voltage range is 3.8-2.0V, the constant current charging is firstly carried out to 3.8V under the 0.1c multiplying power (0.1mA), then the constant voltage charging is carried out to 3.8V (the cut-off voltage is 0.05mA), the discharging current is discharged to 2.0V under the 0.1mA, and the discharging specific capacity is calculated.
The testing process of the discharge specific capacity after 20 times of circulation comprises the following steps: all the batteries are in a thermostat at 45 ℃, and the charging and discharging voltage ranges from 3.8V to 2.0V. Charging for the 20 th time: and under the multiplying power of 0.1c (0.1mA), charging to 3.8V at constant current, then charging at constant voltage, stopping at 0.05mA for voltage, discharging to 2.0V for current of 0.1mA, and calculating the specific discharge capacity of the 20 th time.
TABLE 4
Figure BDA0002088833080000151
As can be seen from Table 4, the all-solid-state lithium ion battery can obtain higher battery cycle performance and specific capacity, wherein under the optimal condition, the first discharge specific capacity can reach 146-150 mAh/g, and the discharge specific capacity after 20 cycles can reach 145-149 mAh/g.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (16)

1. An all-solid electrolyte composition comprising PVDF-HFP, perfluoropolyether, and a first lithium salt; the content of fluorine in the perfluoropolyether is 40-90 wt%;
the molecular weight of the perfluoropolyether is 1,000-5,000 g/mol;
the molecular weight of the PVDF-HFP is 100,000-800,000 g/mol;
the content of the perfluoropolyether is 5 to 600 parts by weight with respect to 100 parts by weight of PVDF-HFP.
2. The composition according to claim 1, wherein the first lithium salt is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of PVDF-HFP.
3. The composition according to claim 2, wherein the perfluoropolyether is contained in an amount of 10 to 400 parts by weight and the first lithium salt is contained in an amount of 30 to 80 parts by weight, relative to 100 parts by weight of PVDF-HFP.
4. The composition according to claim 3, wherein the perfluoropolyether is contained in an amount of 30 to 200 parts by weight and the first lithium salt is contained in an amount of 40 to 60 parts by weight, relative to 100 parts by weight of PVDF-HFP.
5. The composition according to any one of claims 1 to 4, wherein the perfluoropolyether has a fluorine content of 50 to 80 wt.%.
6. The composition of any of claims 1-4, wherein the perfluoropolyether has a molecular weight of 1000 to 4000 g/mol.
7. The composition of any of claims 1-4, wherein the perfluoropolyether is a functionalized perfluoropolyether.
8. The composition of claim 7, wherein the functionalization is selected from silane coupling agent modification.
9. The composition of claim 8, wherein the functionalization is one or more of a silane coupling agent with an alcoholic hydroxyl group and a silane coupling agent with a carbon-carbon double bond.
10. The composition according to any one of claims 1 to 4, wherein the molecular weight of PVDF-HFP is between 100,000 and 700,000 g/mol.
11. The composition according to any one of claims 1 to 4, wherein the PVDF-HFP has a content of structural units derived from vinylidene fluoride of 75 to 90 mol% and a content of structural units derived from hexafluoropropylene of 10 to 25 mol%.
12. The composition of any of claims 1-4, wherein the first lithium salt is LiN (CF)3SO2)2、LiClO4、LiBF4、LiPF6、LiCF3SO3And LiN (CF)3SO2)3One or more of (a).
13. An all-solid-state electrolyte comprising the composition of any one of claims 1-12.
14. An all-solid-state electrolyte prepared from the composition of any one of claims 1-12.
15. An electrode comprising the composition of any one of claims 1-12.
16. An all-solid lithium ion battery comprising the all-solid electrolyte of claim 13 or 14 and the electrode of claim 15.
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