CN114512668A - Electrode binder and preparation method thereof, electrode, lithium battery and vehicle - Google Patents

Electrode binder and preparation method thereof, electrode, lithium battery and vehicle Download PDF

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CN114512668A
CN114512668A CN202011281531.4A CN202011281531A CN114512668A CN 114512668 A CN114512668 A CN 114512668A CN 202011281531 A CN202011281531 A CN 202011281531A CN 114512668 A CN114512668 A CN 114512668A
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lithium
equal
electrode
ionic liquid
ltoreq
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CN114512668B (en
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袁涛
马永军
郭姿珠
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BYD 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
    • C08G12/04—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
    • C08G12/06—Amines
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
    • C08G12/04—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
    • C08G12/06—Amines
    • C08G12/08—Amines aromatic
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The application discloses electrode binder and preparation method, electrode, lithium cell and vehicle thereof, and the electrode binder comprises: the ionic liquid polymer comprises the following structural units:
Figure DDA0002780966800000011
or

Description

Electrode binder and preparation method thereof, electrode, lithium battery and vehicle
Technical Field
The invention relates to the technical field of lithium batteries, in particular to an electrode binder, a preparation method thereof, an electrode, a lithium battery and a vehicle.
Background
The electrode slurry of important components of the lithium battery comprises: positive/negative electrode active materials, conductive agents, binders, solvents, and other additives. The electrode slurry is coated on the surface of the current collector and dried to prepare the electrode. The binder is used as an important component of the lithium ion battery, mainly has the function of adhering an electrode active substance and a conductive agent on the surface of a current collector, and the performance of the binder directly influences the electrochemical performance of the lithium battery.
Existing binders include: polyvinylidene fluoride (PVDF), polyacrylates, styrene-butadiene rubber (SBR), etc., although having a binding effect, cannot effectively conduct lithium ions, and the existing crystalline binder is easily swelled in an electrolyte during use, and electrode slurry is easily dropped from a current collector due to internal stress of an electrode, thereby reducing the performance of a lithium battery.
Disclosure of Invention
In view of the above-mentioned defects or shortcomings in the prior art, it is desirable to provide an electrode binder, a method for preparing the same, an electrode, a lithium battery and a vehicle, so that the binder has good binding effect and lithium ion conducting effect, and simultaneously, the problems of swelling of the binder and falling-off of electrode slurry can be prevented, and the performance of the lithium battery can be improved.
In a first aspect, the present invention provides an electrode binder comprising an ionic liquid polymer having the following structural units:
Figure BDA0002780966790000021
wherein R is1And R3Each independently is any one of bistrifluoromethylsulfonate iminium, bistrifluorosulfoniminium, perchlorate, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, dioxaoxalato borate, difluorooxalato borate or trifluoromethylsulfonate;
R2and R6Each independently is
Figure BDA0002780966790000022
Figure BDA0002780966790000023
Any one of (a);
R4and R5Each independently is any one of an H atom or an F atom;
m is any integer between 0 and 10; n and j are each independently any integer between 1 and 100; i is any integer between 0 and 100;
x, y and z are each independently any decimal number between 0 and 1, and x + y + z is equal to 1.0;
a, b and c are each independently any decimal number between 0 and 1, and a + b + c is equal to 1.0.
As an optional scheme, x is more than or equal to 0.6 and less than or equal to 1.0, y is more than 0 and less than or equal to 0.2, and z is more than 0 and less than or equal to 0.2; a is more than or equal to 0.6 and less than or equal to 1.0, b is more than 0 and less than or equal to 0.2, and c is more than 0 and less than or equal to 0.2.
As an optional scheme, x is more than or equal to 0.6 and less than or equal to 0.9, y is more than 0 and less than or equal to 0.2, and z is more than or equal to 0.1 and less than or equal to 0.2; a is more than or equal to 0.6 and less than or equal to 0.9, b is more than 0 and less than or equal to 0.2, and c is more than or equal to 0.1 and less than or equal to 0.2.
Optionally, the molecular weight of the ionic liquid polymer is 10000-500000.
In a second aspect, the present invention provides a method for preparing the electrode binder of the first aspect, comprising the steps of:
adding acid liquor into the diamine-terminated compound, and dissolving in a solvent to obtain a mixed liquor I;
dropwise adding the mixed solution of formaldehyde and acetaldehyde into the mixed solution I, heating and reacting to obtain a mixed solution II;
cooling, distilling under reduced pressure and washing the mixed solution II to obtain an ionic liquid polymer containing acid radical balance anions;
dissolving an ionic liquid polymer containing acid radical balance anions in water to obtain a mixed solution III, and dropwise adding the mixed solution III into an aqueous solution of an anion exchanger to react to generate a precipitate;
and washing and drying the precipitate to obtain the electrode binder.
Optionally, the acid solution is any one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.
Alternatively, the di-amino-terminated compound is selected from substituted or unsubstituted
Figure BDA0002780966790000031
Figure BDA0002780966790000032
At least one of;
wherein p is any integer between 1 and 10; q is any integer between 1 and 100; k is any integer between 1 and 100; the substituents in the diamine-terminated compound are independently selected from halogen, hydroxyl, carbonyl, cyano, C1-C6Alkyl of (C)6-C12Aryl or C of6-C12At least one of cycloalkyl groups of (a).
Alternatively, the solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N-dimethylformamide, sulfolane, or dimethylsulfoxide.
Optionally, the anion exchanger is any one of lithium bistrifluoromethylsulfonate imide, lithium bistrifluorosulfonimide, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate or lithium trifluoromethanesulfonate.
In a third aspect, the present invention provides an electrode for a lithium battery, comprising: a current collector and an active material layer formed on a surface of the current collector, the active material layer including the electrode binder of the first aspect.
In a fourth aspect, the present invention provides a lithium battery comprising the electrode for a lithium battery of the third aspect.
In a fifth aspect, the present invention provides a vehicle comprising the lithium battery of the fourth aspect.
According to the electrode binder provided by the application, the electrode binder is an ionic liquid polymer, the polymer chain in the ionic liquid polymer enables the binder to have a good binding effect, the imidazole cation in the ionic liquid polymer has a large coulombic force and can act with lithium ions, so that the lithium ions are conducted, and the flexibility and tensile strength of the binder are improved due to the fact that the flexible PEG chain segment and the rigid cyclohexane or benzene ring chain segment are arranged; compared with the existing binder, the binder has good binding effect and ionic conductivity, effectively improves the problems of swelling of the binder and falling of electrode slurry, and further improves the specific capacity, the rate capability and the cycling stability of the lithium battery.
Detailed Description
The present application will be described in further detail with reference to examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the invention are shown in the embodiments.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail with reference to examples.
Embodiments of the present invention provide an electrode binder comprising an ionic liquid polymer comprising a cation and an anion, the cation being an imidazolium cation on the polymer backbone.
Compared with the traditional binder, the ionic liquid polymer has good cohesiveness and is not easy to crystallize, so that the influence of crystallization of the binder on ion conduction in the use process of the lithium battery is avoided, and meanwhile, partial or complete falling of electrode slurry from a current collector is also avoided, and the capacity of the lithium battery is reduced;
in addition, the cation of the ionic liquid polymer is imidazole cation on the main chain of the polymer, and the imidazole cation has higher coulombic force and can interact with lithium ions, so that the polymer has good ionic conductivity, is beneficial to the diffusion and transmission of the lithium ions in an electrode material, reduces the internal resistance of the battery, and improves the specific capacity, the rate capability and the cycling stability of the battery.
Further, the structural units of the ionic liquid polymer are as follows:
Figure BDA0002780966790000051
wherein R is1And R3Each independently is bistrifluoromethylsulfonatoAny one of an amine group, a bisfluorosulfonylimide group, a perchlorate group, a hexafluorophosphate group, a hexafluoroarsenate group, a tetrafluoroborate group, a dioxaoxalato borate group, a difluorooxalato borate group, or a trifluoromethylsulfonate group;
R2and R6Each independently is
Figure BDA0002780966790000052
Figure BDA0002780966790000053
Any one of (a);
R4and R5Each independently is any one of an H atom or an F atom;
m is any integer between 0 and 10; n and j are each independently any integer between 1 and 100; i is any integer between 0 and 100;
x, y and z are each independently any decimal number between 0 and 1, which is used for representing the molar ratio between each structural unit, and x + y + z is equal to 1.0;
a, b and c are each independently any decimal between 0 and 1 for representing the molar ratio between each structural unit, and a + b + c is equal to 1.0.
It should be noted that when y and b in the structural unit of the ionic liquid polymer are not equal to 0, the ionic liquid polymer contains a PEG (polyethylene glycol) segment, which is beneficial to conducting lithium ions, and provides flexibility for the ionic liquid polymer, so that the ionic liquid polymer can adapt to the volume change of an active substance, thereby improving the charge-discharge cycle stability of the electrode; when y and b in the structural unit of the ionic liquid polymer are equal to 0, the ionic liquid polymer does not contain a PEG (polyethylene glycol) segment, and the oxidation resistance and the ionic conductivity of the ionic liquid polymer are further improved under the synergistic effect of imidazole cations and/or fluorine-containing segments on the main chain of the polymer.
The introduction of rigid structures such as cyclohexane, benzene, biphenyl and the like can improve the tensile strength of the polymer and prevent the binder from swelling in the electrolyte;
the structure of the polymer for ionic liquids is formula II when R4And R5When any one of the F atoms is F atom, namely, a fluorine-containing chain segment is introduced into the ionic liquid polymer, which is beneficial to improving the oxidation resistance of the ionic liquid polymer;
the structure of the ionic liquid polymer is shown in formula II, when a in the structure of the ionic liquid polymer is not equal to 0, the ionic liquid polymer contains a chain segment of amido bond, and the amido bond is favorable for further improving the bonding property of the ionic liquid polymer;
the structural unit of the ionic liquid polymer can show that the ionic liquid polymer does not contain a crystalline chain segment, and is favorable for improving the wettability of the electrode to electrolyte.
Furthermore, x is more than or equal to 0.6 and less than or equal to 1.0, y is more than 0 and less than or equal to 0.2, and z is more than 0 and less than or equal to 0.2; a is more than or equal to 0.6 and less than or equal to 1.0, b is more than 0 and less than or equal to 0.2, and c is more than 0 and less than or equal to 0.2; for example, x and a are each independently 0.6, 0.7, 0.8, 0.85, 0.9, 0.95, 1.0, etc.; y and b are each independently 0.1, 0.15, 0.18, 0.2, etc.; z and c are each independently 0.1, 0.15, 0.18, 0.2, etc.;
preferably, x is more than or equal to 0.6 and less than or equal to 0.9, y is more than 0 and less than or equal to 0.2, and z is more than or equal to 0.1 and less than or equal to 0.2; a is more than or equal to 0.6 and less than or equal to 0.9, b is more than 0 and less than or equal to 0.2, and c is more than or equal to 0.1 and less than or equal to 0.2. The value ranges of x, y and z, and a, b and c disclosed by the invention are favorable for adjusting the contents of an imidazole cation chain segment, a PEG chain segment, a fluorine-containing chain segment and a rigid chain segment in the ionic liquid polymer, and further controlling the cohesiveness, flexibility, ionic conductivity and tensile strength of the ionic liquid polymer, so that the ionic liquid has the optimal performance.
Furthermore, the molecular weight of the ionic liquid polymer is 10000-500000. For example: the ionic liquid polymer may have a molecular weight of 10000, 15000, 20000, 30000, 50000, 100000, 180000, 250000, 30000, 360000, 400000, 430000, 480000, 500000, or the like. The specific molecular weight is not limited in the examples of the present invention.
In conclusion, the electrode binder disclosed by the invention has good binding property and ionic conductivity, is beneficial to the diffusion and transmission of lithium ions in an electrode material, reduces the internal resistance of a battery, and further improves the specific capacity, the rate capability and the cycling stability of the battery;
in addition, the content of each functional group is controlled, so that the conductivity, flexibility and tensile strength of polymer lithium ions can be controlled, the electrode binder can effectively conduct the lithium ions, the active material can be prevented from falling off by adapting to the volume change of the active material, and the binder can be prevented from swelling in electrolyte, so that the charge-discharge cycle stability of the electrode is improved.
In a second aspect, embodiments of the present invention provide a method for preparing the electrode binder of the first aspect, including the steps of:
adding acid liquor into the mixture of the diamine-terminated compounds, and dissolving in a solvent to obtain a mixed liquor I;
dropwise adding the mixed solution of formaldehyde and acetaldehyde into the mixed solution I, heating and reacting to obtain a mixed solution II;
cooling, distilling under reduced pressure and washing the mixed solution II to obtain an ionic liquid polymer containing acid radical balance anions;
dissolving an ionic liquid polymer containing acid radical balance anions in water to obtain a mixed solution III, and dropwise adding the mixed solution III into an aqueous solution of an anion exchanger to react to generate a precipitate;
and washing and drying the precipitate to obtain the electrode binder.
It should be noted that, in the following description,
the acid liquor is added for the purpose of providing an acidic condition, and acid radical ions are used as balancing anions of cations for synthesizing the ionic liquid polymer and are beneficial to ion exchange with other ions;
a mixture of formaldehyde and acetaldehyde is used for reacting with a diamine-terminated compound under acidic conditions to generate a polymer main chain containing an imidazole group;
wherein, the diamine-terminated compound may be one kind, or may be a mixture of two or more kinds of diamine-terminated compounds, wherein each diamine-terminated compound is mixed according to a certain proportion, and the proportion is not specifically limited herein; the diamine-terminated compound can also contain amido bond; the structures of ionic liquid polymers generated by different diamine-terminated compounds are different, and the diamine-terminated compounds are adaptively selected according to the specific performance of the required ionic liquid polymers;
the generated ionic liquid polymer containing the acid radical balance anions is dissolved in water for ion exchange, so that the ionic liquid polymer is prevented from being dissolved in an organic solvent due to the adoption of the organic solvent, and is not easy to separate and remove impurities.
As an example of this, the following is given,
adding acetic acid into
Figure BDA0002780966790000081
Wherein m is 2, and dissolving in water to obtain a mixed solution I;
dropwise adding the mixed solution of formaldehyde and acetaldehyde into the mixed solution I under the condition of ice-water bath, heating to 100 ℃, and reacting for 2 hours to obtain a mixed solution II;
cooling, distilling under reduced pressure and washing the mixed solution II to obtain an ionic liquid polymer containing acetate balance anions;
dissolving an ionic liquid polymer containing acetate group balance anions in water to obtain a mixed solution III, dropwise adding the mixed solution III into an aqueous solution of lithium bistrifluoromethylsulfonyl imide, and reacting to generate a precipitate;
washing and drying the precipitate to obtain the electrode binder with a structural formula shown in
Figure BDA0002780966790000091
Further, the acid solution is any one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.
Further, the diamine-terminated compound is selected from substituted or unsubstituted
Figure BDA0002780966790000092
Figure BDA0002780966790000093
At least one of;
wherein p is any integer between 1 and 10; q is any integer between 1 and 100; k is any integer between 1 and 100; the diamine-terminated compound is independently selected from halogen, hydroxyl, carbonyl, cyano and C1-C6Alkyl of (C)6-C12Aryl or C of6-C12At least one of cycloalkyl groups of (a).
It should be noted that, in the following description,
the halogen is selected from one of fluorine, chlorine and bromine; c1-C6The alkyl of (A) is selected from one of methyl, ethyl, propyl, isopropyl, butyl or tert-butyl; c6-C12The aryl group of (a) is selected from one of phenyl, naphthyl or biphenyl; c6-C12The cycloalkyl group of (a) is selected from cyclohexyl or dicyclohexyl.
Further, the solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N-dimethylformamide, sulfolane, or dimethylsulfoxide.
Further, the conditions for obtaining mixture II were: the temperature is 80-120 ℃, and the time is 0.5-4 h. For example, the temperature is 80 ℃, 90 ℃, 100 ℃, 110 ℃ or 120 ℃ or the like; the time is 0.5h, 1h, 2h, 3h or 4h and the like. The specific reaction temperature and time are not limited in the embodiments of the present invention. The condition of the reaction of the mixture of formaldehyde and acetaldehyde disclosed in the embodiment of the invention and the diamine-terminated compound under the acidic condition is favorable for promoting the reaction and improving the yield of reactants.
Further, the anion exchanger is any one of lithium bistrifluoromethylsulfonate imide, lithium bistrifluorosulfonimide, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, or lithium trifluoromethanesulfonate.
In a third aspect, an embodiment of the present invention provides an electrode for a lithium battery, including: a current collector and an active material layer formed on a surface of the current collector, the active material layer including the electrode binder of the first aspect. It will be understood by those skilled in the art that the electrode of the lithium battery has all the features and advantages of the electrode binder described above, and thus, will not be described in detail herein.
It should be noted that, in the following description,
here, the electrode of the lithium battery may be a positive electrode or a negative electrode.
In a specific example, an electrode for a lithium battery was prepared by the following procedure:
mixing an active material, a binder and a conductive agent, and dispersing the mixture in a solvent to obtain electrode slurry, namely an active material layer;
and coating the active material layer on a current collector, and heating and drying to obtain the electrode of the lithium battery.
Wherein, for the positive electrode of the lithium battery, the active material in the active material layer is selected from LiCoO2、LiNiO2、LiCoxNi1-xO2(0≤x≤1)、LiCoxNi1-x-yAlyO2(0≤x≤1，0≤y≤1)、LiCoxNi1-x-yMnyO2(0≤x≤1，0≤y≤1)、LiMn2O4、LiFePO4、Li3V2(PO4)3、Li3V3(PO4)3、LiVPO4F、Li2CuO2、Li5FeO4At least one of;
for the negative electrode of a lithium battery, the active material in the active material layer is selected from silicon-based materials (e.g., Si, SiO)xSi-C composite, Si-Q alloy, etc.), lithium titanate or graphite;
the mass ratio of the active material to the binder to the conductive agent is 70-95: 2-20: 3-10;
the dosage of the solvent is 1-50 times of the total weight of the active material, the binder and the conductive agent;
the conductive agent is at least one of conductive graphite, carbon black, acetylene black, carbon nanorods, carbon nanotubes, graphene and Ketjen black;
the solvent is at least one of N-methyl pyrrolidone, N-methyl formamide, N-methyl acetamide, N-dimethyl formamide, sulfolane and dimethyl sulfoxide.
In a fourth aspect, embodiments of the present invention provide a lithium battery including an electrode of the lithium battery of the third aspect. It will be appreciated by those skilled in the art that the electrode of the lithium battery has all the features and advantages of the electrode binder described above and will not be described in excessive detail herein. In general, the lithium battery provided by the embodiment of the invention has good specific capacity and cycling stability.
The lithium battery comprises a battery shell, a pole core and electrolyte, wherein the pole core and the electrolyte are contained in the battery shell in a sealing mode, and the pole core comprises a positive pole, a negative pole and a diaphragm located between the positive pole and the negative pole.
The positive electrode is the corresponding positive electrode; the negative electrode is the corresponding negative electrode; the diaphragm is selected from one of polyolefin microporous membrane (PP), polyethylene felt (PE), glass fiber felt or superfine glass fiber paper or PP/PE/PP; the electrolyte contains lithium salt and non-aqueous solvent, wherein the lithium salt is selected from one or more of lithium bistrifluoromethylsulfonate imide, lithium difluorosulfonyl imide, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate or lithium trifluoromethanesulfonate; the non-aqueous solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene glycol dimethyl ether, 1, 3-dioxolane, 1, 4-dioxane, gamma-butyrolactone, N-methyl pyrrolidone, N-methyl formamide, N-methyl acetamide, acetonitrile, N-dimethyl formamide, sulfolane, dimethyl sulfoxide, dimethyl sulfite and other cyclic organic esters containing fluorine, sulfur or unsaturated bonds; the concentration of the lithium salt in the electrolyte is 0.1-10 mol/L, preferably 0.5-4 mol/L.
In a fifth aspect, the present disclosure provides a vehicle comprising the lithium battery of the fourth aspect. For example, a plurality of battery packs composed of the lithium batteries described above may be included. Thus, the vehicle has all of the features and advantages of the lithium battery described above, and will not be described in detail herein.
The present invention is illustrated below by means of specific examples, which are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
Example 1
(1) Preparation of electrode Binder (Ionic liquid Polymer)
Figure BDA0002780966790000121
Wherein TFSI represents bis (trifluoromethyl) sulfonyl imide, and the molar ratio of the three structural units is 8:1: 1;
the specific process is as follows:
adding acetic acid into a diamine-based end-capping compound
Figure BDA0002780966790000122
Figure BDA0002780966790000123
Wherein m is 2, n is 2, and the ratio of m to n is 8:1: 1; dissolving in water to obtain a mixed solution I;
dropwise adding the mixed solution of formaldehyde and acetaldehyde into the mixed solution I under the condition of ice-water bath, heating to 100 ℃, and reacting for 2 hours to obtain a mixed solution II;
cooling, distilling under reduced pressure and washing the mixed solution II to obtain an ionic liquid polymer containing acetate balance anions;
dissolving an ionic liquid polymer containing acetate group balance anions in water to obtain a mixed solution III, dropwise adding the mixed solution III into an aqueous solution of lithium bistrifluoromethylsulfonyl imide, and reacting to generate a precipitate;
washing and drying the precipitate to obtain the electrode binder with a structural formula shown in
Figure BDA0002780966790000124
(2) Electrode preparation
Preparation of the positive electrode: subjecting LiCoO to condensation2The ionic liquid polymer and the acetylene black are uniformly mixed according to the mass ratio of 90:5:5 and then are dispersed in an N-methyl pyrrolidone solvent to obtain the ionic liquid polymerCoating the electrode slurry on an aluminum foil, and drying for 24 hours at the temperature of 80 ℃ in vacuum, wherein the coating thickness is 100 mu m;
preparation of a negative electrode: uniformly mixing graphite, the ionic liquid polymer and acetylene black in a mass ratio of 90:5:5, dispersing the mixture in an N-methylpyrrolidone solvent to obtain electrode slurry, coating the electrode slurry on a copper foil, and drying the copper foil at 80 ℃ in vacuum for 24 hours, wherein the coating thickness is 100 micrometers.
(3) Lithium battery preparation
Assembly of button cell CR 2025: taking the above positive electrode (phi 15mm), the above negative electrode (phi 16mm), PE separator (phi 19mm), and 1mol/L LiPF6EC/DMC/DEC (v/v/v-1/1/1) electrolyte was assembled into CR2025 button cells. This procedure is carried out in an argon-filled glove box (content O)2≤0.5ppm、H2O is less than or equal to 0.5 ppm).
Example 2
This example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000131
Wherein the molar ratio of the three structural units is 7:2: 1;
the diamine-terminated compound is
Figure BDA0002780966790000132
Figure BDA0002780966790000133
Wherein m is 2 and n is 2, 1.
Example 3
This example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000134
Wherein the molar ratio of the three structural units is 6:3: 1;
the diamine-terminated compound is
Figure BDA0002780966790000141
Figure BDA0002780966790000142
Wherein m is 2 and n is 2, and the ratio of the three is 6:3: 1.
Example 4
This example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000143
Wherein the molar ratio of the three structural units is 8:1: 1;
the diamine-terminated compound is
Figure BDA0002780966790000144
Figure BDA0002780966790000145
Wherein i is 4, n is 2, R4，R5All are F atoms, and the ratio of the three is 8:1: 1.
Example 5
This example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000146
Wherein the molar ratio of the three structural units is 7:2: 1;
the diamine-terminated compound is
Figure BDA0002780966790000147
Figure BDA0002780966790000148
Wherein i is 4, n is 2, R4，R5All are F atoms, and the ratio of the three is 7:2: 1.
Example 6
This example differs from example 1 in that:
preparation method of the compoundLiquid polymers
Figure BDA0002780966790000151
Wherein the molar ratio of the three structural units is 6:3: 1;
the diamine-terminated compound is
Figure BDA0002780966790000152
Figure BDA0002780966790000153
Wherein i is 4, n is 2, R4，R5All are F atoms, and the ratio of the three is 6:3: 1.
Comparative example 1
This comparative example differs from example 1 in that: the electrode binder is PVDF.
Comparative example 2
This comparative example differs from example 1 in that: the electrode binder is PMMA (polymethyl methacrylate).
Comparative example 3
This comparative example differs from example 1 in that: the electrode binder was SBR (styrene-butadiene rubber).
Comparative example 4
This comparative example differs from example 1 in that: preparation of Ionic liquid polymers
Figure BDA0002780966790000154
Wherein TFSI represents bis (trifluoromethylsulfonyl) imide.
Comparative example 5
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000155
Wherein the molar ratio of the two structural units is 9: 1;
the diamine-terminated compound is
Figure BDA0002780966790000161
Wherein m is 2And are and
Figure BDA0002780966790000162
and the ratio of the two is 9: 1.
Comparative example 6
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000163
Wherein the molar ratio of the two structural units is 8: 2;
the diamine-terminated compound is
Figure BDA0002780966790000164
Wherein m is 2, and
Figure BDA0002780966790000165
and the ratio of the two is 8: 2.
Comparative example 7
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000166
Wherein the molar ratio of the two structural units is 8: 2;
the diamine-terminated compound is
Figure BDA0002780966790000167
Wherein m is 2, n is 2, and the ratio of the two is 8: 2.
Comparative example 8
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000168
Wherein TFSI represents bis (trifluoromethyl) sulfonimide;
the diamine-terminated compound is
Figure BDA0002780966790000169
Wherein i is 4, R4，R5Are all F atoms.
Comparative example 9
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000171
Wherein the molar ratio of the two structural units is 9: 1;
the diamine-terminated compound is
Figure BDA0002780966790000172
Figure BDA0002780966790000173
Wherein i is 4, R4，R5Both are F atoms and the ratio of the two is 9: 1.
Comparative example 10
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000174
Wherein the molar ratio of the two structural units is 8: 2;
the diamine-terminated compound is
Figure BDA0002780966790000175
Figure BDA0002780966790000176
Wherein i is 4, R4，R5Both are F atoms and the ratio of both is 8: 2.
Comparative example 11
This comparative example differs from example 1 in that:
preparation of Ionic liquid polymers
Figure BDA0002780966790000181
Wherein the molar ratio of the two structural units is 8: 2;
the diamine-terminated compound is
Figure BDA0002780966790000182
Figure BDA0002780966790000183
Wherein i is 4, n is 2, R4，R5Both are F atoms and the ratio of both is 8: 2.
The lithium batteries prepared in the above examples 1 to 6 and comparative examples 1 to 11 were subjected to the following performance tests for characterizing the electrochemical properties of the electrode binder.
(1) Battery rate capability test
After the cell was assembled, it was first charged from 3.0V to 4.2V at a rate of 0.05C, then left to stand for 5 minutes, and then discharged from 4.2V to 3.0V at a rate of 0.05C, and the above process was cycled three times. Then, the cell was charged at a constant current of 3.0V to 4.2V at a rate of 0.1C, and was cut off at a constant voltage of 4.2V to 0.01C, and then left to stand for 5 minutes, and finally discharged at rates of 0.1C, 0.5C, 1C, 2C, 5C, and 10C to 3.0V, respectively, and the test results are shown in Table 1.
(2) Battery cycle performance test
After the cell was assembled, it was first charged from 3.0V to 4.2V at a rate of 0.05C, then left to stand for 5 minutes, and then discharged from 4.2V to 3.0V at a rate of 0.05C, and the above process was cycled three times. Then constant current charging from 3.0V to 4.2V at a rate of 0.5C, constant voltage charging to 0.01C at 4.2V, stopping, then standing for 5 minutes, finally discharging to 3.0V at a rate of 0.5C, and finally standing for 5 minutes. The process is circulated 200 times. The results of 200 cycles of the above battery are shown in table 1.
TABLE 1 results of performance test of lithium batteries prepared in examples 1 to 6 and comparative examples 1 to 11
Figure BDA0002780966790000191
From the results shown in table 1, the batteries prepared in examples 1 to 6 were superior to the batteries prepared in comparative examples 1 to 3 in both rate performance and cycle performance, indicating that the electrode binder prepared according to the present invention is advantageous in improving the performance of a lithium battery, compared to the conventional binder.
By combining the results in table 1 and the structural analysis of the electrode binder of the embodiment of the present invention, the electrode binder of the embodiment of the present invention improves the ionic conductivity of the binder, facilitates the diffusion and transmission of lithium ions in the electrode material, and reduces the internal resistance of the battery, thereby improving the specific capacity, the rate capability and the cycling stability of the battery. For example: according to the structures of the embodiment 1 and the embodiment 4, the performance of the lithium battery is improved by introducing the amido bond chain segment, and the reason that the amido bond chain segment is beneficial to further improving the bonding performance of the ionic liquid polymer is probably analyzed; from the results of comparative example 4 and comparative example 5, it is understood that the introduction of the benzene-containing segment improves the performance of the battery, and it is analytically possible that the benzene-containing segment can increase the tensile strength of the polymer and prevent the binder from swelling in the electrolyte; from the results of comparative example 4 and comparative example 7, it is understood that the introduction of the PEG segment improves the performance of the battery, and it is analytically possible that the PEG segment facilitates the conduction of lithium ions while providing flexibility to the ionic liquid polymer, so that it can adapt to the volume change of the active material, thereby improving the charge-discharge cycle stability of the electrode.
The rate performance and cycle performance of the batteries prepared in comparative example 1 and comparative examples 4 to 7 can be obtained from table 1: the battery of example 1 is superior to the batteries of comparative examples 4 to 7 in both rate performance and cycle performance. The ionic liquid polymer of the embodiment of the invention simultaneously comprises the imidazole cation chain segment, the flexible PEG chain segment and the rigid cyclohexane or benzene ring chain segment, and under the synergistic action of the imidazole cation chain segment, the flexible PEG chain segment and the rigid cyclohexane or benzene ring chain segment, the ionic liquid polymer is favorable for improving the adhesive property, flexibility, tensile strength and ionic conductivity of the ionic liquid polymer, and further improving the performance of the lithium battery.
Similarly, the results of rate performance and cycle performance of the batteries prepared in example 1 and comparative examples 8 to 11 show that the ionic liquid polymer has synergistic effects on the imidazolyl segment (or fluorine atom or amido bond), the flexible PEG segment and the rigid cyclohexane benzene ring segment, which is beneficial to improving the adhesion, flexibility, tensile strength and ionic conductivity of the ionic liquid polymer, and further improving the performance of the lithium battery.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.

Claims (12)

1. An electrode binder comprising an ionic liquid polymer having the following structural units:
Figure FDA0002780966780000011
or
Figure FDA0002780966780000012
Wherein R is1And R3Each independently is bistrifluoromethylsulfonate iminium, bistrifluorosulfonimide, perchlorate, hexafluorophosphate, hexafluoroarsenate, tetrafluoroborate, dioxaoxalato borate, difluorooxalato borate orAny one of a trifluoromethyl sulfonate;
R2and R6Each independently is
Figure FDA0002780966780000013
Figure FDA0002780966780000014
Any one of (a);
R4and R5Each independently is any one of an H atom or an F atom;
m is any integer between 0 and 10; n and j are each independently any integer between 1 and 100; i is any integer between 0 and 100;
x, y and z are each independently any decimal number between 0 and 1, and x + y + z is equal to 1.0;
a, b and c are each independently any decimal number between 0 and 1, and a + b + c is equal to 1.0.
2. The electrode binder as claimed in claim 1, wherein x is 0.6. ltoreq. x.ltoreq.1.0, y is 0. ltoreq. y.ltoreq.0.2, and z is 0. ltoreq. z.ltoreq.0.2; a is more than or equal to 0.6 and less than or equal to 1.0, b is more than 0 and less than or equal to 0.2, and c is more than 0 and less than or equal to 0.2.
3. The electrode binder as claimed in claim 2, wherein x is 0.6. ltoreq. x.ltoreq.0.9, y is 0. ltoreq.0.2, and z is 0.1. ltoreq. z.ltoreq.0.2; a is more than or equal to 0.6 and less than or equal to 0.9, b is more than 0 and less than or equal to 0.2, and c is more than or equal to 0.1 and less than or equal to 0.2.
4. The electrode binder as claimed in any one of claims 1 to 3, wherein the ionic liquid polymer has a molecular weight of 10000 to 500000.
5. A method for preparing an electrode binder according to any one of claims 1 to 4, comprising the steps of:
adding acid liquor into the diamine-terminated compound, and dissolving in a solvent to obtain a mixed liquor I;
dropwise adding the mixed solution of formaldehyde and acetaldehyde into the mixed solution I, heating and reacting to obtain a mixed solution II;
cooling, distilling under reduced pressure and washing the mixed solution II to obtain an ionic liquid polymer containing acid radical balance anions;
dissolving the ionic liquid polymer containing the acid radical balance anions in water to obtain a mixed solution III, and dropwise adding the mixed solution III into an aqueous solution of an anion exchanger to react to generate a precipitate;
and washing and drying the precipitate to obtain the electrode binder.
6. The method according to claim 5, wherein the acid solution is any one of acetic acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
7. The method of claim 5, wherein the bis-amine-based end-capping compound is selected from substituted or unsubstituted
Figure FDA0002780966780000021
Figure FDA0002780966780000022
Figure FDA0002780966780000031
At least one of;
wherein p is any integer between 1 and 10; q is any integer between 1 and 100; k is any integer between 1 and 100; the substituents in the diamine-terminated compound are respectively and independently selected from halogen, hydroxyl, carbonyl, cyano and C1-C6Alkyl of (C)6-C12Aryl or C of6-C12At least one of cycloalkyl groups of (a).
8. The method according to claim 5, wherein the solvent is any one of water, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, N-dimethylformamide, sulfolane, or dimethylsulfoxide.
9. The method according to claim 5, wherein the anion exchanger is any one of lithium bistrifluoromethylsulfonate, lithium bistrifluorosulfonimide, lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate, lithium difluorooxalate or lithium trifluoromethanesulfonate.
10. An electrode for a lithium battery, comprising: a current collector and an active material layer formed on a surface of the current collector, wherein the active material layer comprises the electrode binder according to any one of claims 1 to 4.
11. A lithium battery comprising an electrode for a lithium battery according to claim 10.
12. A vehicle characterized by comprising the lithium battery of claim 11.
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