CN117012910A - Composite material, preparation method and application thereof - Google Patents

Composite material, preparation method and application thereof Download PDF

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Publication number
CN117012910A
CN117012910A CN202210468809.1A CN202210468809A CN117012910A CN 117012910 A CN117012910 A CN 117012910A CN 202210468809 A CN202210468809 A CN 202210468809A CN 117012910 A CN117012910 A CN 117012910A
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coating layer
ionic
core
composite material
polymer
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汤哲浩
沙玉静
夏圣安
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to CN202210468809.1A priority Critical patent/CN117012910A/en
Priority to PCT/CN2023/090709 priority patent/WO2023208007A1/en
Publication of CN117012910A publication Critical patent/CN117012910A/en
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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • 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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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The embodiment of the application provides a composite material, and a preparation method and application thereof. The composite material comprises a core and a coating layer coated on the core, wherein the core comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent, the coating layer comprises ionic gel, the ionic gel comprises a polymer and an ionic liquid, and the ionic liquid is dispersed in a three-dimensional network structure formed by the polymer. The coating layer containing the ionic gel exists, so that the stability and electrochemical performance of the core material can be improved, the electrochemical performance of a secondary battery adopting the composite material is further improved, and the product competitiveness is improved.

Description

Composite material, preparation method and application thereof
Technical Field
The application relates to the technical field of batteries, in particular to a composite material and a preparation method and application thereof.
Background
Lithium ion batteries have been widely used in portable electronic products such as mobile phones and notebook computers, new energy automobiles and other fields, the energy density of the lithium ion batteries based on the traditional graphite negative electrode is close to the ceiling, the increasingly-increased endurance and standby demands of people cannot be met, and silicon-based and phosphorus-based negative electrode materials with higher theoretical specific capacity are considered as effective ways for breaking through the high energy density of the lithium secondary batteries. However, the silicon-based and phosphorus-based anode materials are easy to generate larger volume change in the charge and discharge process, so that the anode material particles are pulverized, and the cycle performance and other electrochemical performances of the battery are deteriorated.
At present, the proposal for improving the expansion problem is that an inorganic carbon coating layer, a polymer coating layer or a plurality of coating layers are constructed on the anode material, but the inorganic carbon coating layer has poor toughness and insufficient adhesiveness and cannot bear the volume change of the anode material in the lithium removal and intercalation process permanently; the toughness of the polymer coating layer is better, but the ionic conductivity is poorer, so that the interface impedance of the material is high, which is not beneficial to the capacity exertion and the rate performance reduction of the cathode material. At present, a scheme capable of effectively solving the problem of lithium intercalation and deintercalation expansion of the anode material without reducing capacity exertion and rate performance of the anode material is not found.
Disclosure of Invention
In view of this, the embodiment of the application provides a composite material with an ionic gel coating layer, so as to improve the stability and electrochemical performance of the core material.
The first aspect of the embodiment of the application provides a composite material, which comprises an inner core and a coating layer coated on the inner core, wherein the inner core comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent, the coating layer comprises ionic gel, the ionic gel comprises a polymer and an ionic liquid, and the ionic liquid is dispersed in a three-dimensional network structure formed by the polymer.
In the composite material provided by the embodiment of the application, the core is coated by the coating layer containing the ionic gel, the coating layer is a solid soft material, and has good toughness, certain adhesiveness and excellent ionic conductivity, when the core is the anode active material, the coating layer can better bear the volume change of the anode active material in the lithium intercalation process and expand/shrink along with the core material while the multiplying power performance of the core material is not reduced and the capacity is beneficial to play, the coating layer is not easy to damage/drop, and the whole composite material is not easy to drop from the pole piece, so that the cycle stability of the anode active material is improved. In addition, when the inner core is an anode active material or a lithium supplementing agent, the adhesiveness and the excellent ionic conductivity of the ionic gel coating layer are favorable for keeping stronger bonding force with the inner core, the exertion of the electrochemical performance of the inner core is not influenced, and the good hydrophobicity of the ionic gel coating layer can also improve the water-oxygen stability of the inner core material and the slurry stability in the pulping process.
In an embodiment of the present application, the thickness of the coating layer is 5nm to 50nm. The ionic gel coating layer with proper thickness can ensure that the ionic gel coating layer can stably play the function of the coating layer (such as providing buffer for volume expansion of the core material, ensuring storage or processing stability of the core, and the like), and can not influence the play of the electrochemical performance of the core material due to the excessively thick thickness.
In the embodiment of the application, in the ionic gel, the mass ratio of the polymer is 5% -50%, and the mass ratio of the ionic liquid is 50% -95%. Therefore, the ionic gel without obvious macroscopic phase separation can be formed, and the ionic gel has the advantages of no overlarge strength, good tensile property and excellent adhesive property.
In an embodiment of the application, the polymer comprises structural units of formula (I):
wherein R is 1 Selected from hydrogen, fluorine or methyl, R 2 Selected from the group consisting of hydrogen atoms, fluorine atoms, methyl groups, fluoromethyl groups, - (CH) 2 ) a -Z-, wherein a is an integer from 0 to 6, Z being selected from the group consisting of-COOH, -COOLi, -COONa, -COOK, - (CH) 2 CH 2 O) n H、 -(CH 2 CH 2 O) n CH 3 、-COOR 3 、-CONH 2 、-CONH(R 4 )、-CON(R 5 )(R 6 )；R 3 、R 4 、R 5 、R 6 Independently selected from C 1-6 N is independently selected from integers of 1-20 for each occurrence. When the polymer in the ionic gel coating layer has the structural unit, the polarity of the polymer is larger, and the polymer can be smoothly dissolved in the ionic liquid to obtain the ionic gel without obvious macroscopic phase separation; in addition, can also pass throughRegulation of R 1 、R 1 And the ionic liquid is used for realizing the bonding performance of the ionic gel to different coated core materials.
In an embodiment of the application, the number average molecular weight of the polymer is from 1kDa to 1000kDa. The ionic gel layer containing the polymer has high tensile strength and adhesiveness, and ensures good dispersibility of the polymer in an ionic liquid matrix.
In an embodiment of the present application, the cations in the ionic liquid include one or more of alkyl substituted imidazole cations, alkyl substituted pyrrole cations, alkyl substituted pyridine cations, alkyl substituted thiazole cations, alkyl substituted piperidine cations, alkylammonium cations, and alkylphosphonium cations.
In an embodiment of the present application, the ionic conductivity of the material of the coating layer is 10 at room temperature -4 S·cm -1 The above.
In the embodiment of the application, the breaking elongation of the coating layer is more than 100%, and the breaking strength is in the range of 0.5-5 MPa. These parameters reflect the good toughness and excellent tensile properties of the ionogel coating; the anode active material is coated by the material, is not easy to damage and fall off, can permanently provide buffering of volume expansion for the anode core material, and improves the circulation stability of the material.
In some embodiments of the present application, the coating layer further comprises one or more of a conductive agent, a metal salt of an active metal ion, and a surfactant.
In some embodiments of the application, the coating layer further comprises a carbonization layer comprising a doping element, wherein the doping element is derived from the ionic liquid. The presence of the doped carbide layer can enhance the conductivity of the composite material.
The second aspect of the embodiment of the application provides a preparation method of a composite material, which comprises the following steps:
dispersing a polymer and an ionic liquid into a solvent to obtain an ionic gel precursor solution;
mixing the core material with the ionic gel precursor solution to obtain a mixed material; wherein the core material comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent;
and removing the solvent in the mixed material, and forming a coating layer containing ionic gel on the surface of the core material in the removal process of the solvent to obtain the composite material.
In some embodiments of the application, after removing the solvent, the above preparation method further comprises: and (3) carrying out heat treatment on the solid material obtained after the solvent is removed at the temperature of 50-80 ℃. The heat treatment can enhance the fluidity of the ionic gel on the surface of the core material and promote the coating uniformity of the ionic gel.
In some embodiments of the present application, after forming the coating layer containing the ionic gel, the preparation method further comprises: and (3) carrying out high-temperature calcination treatment on the composite material so as to carbonize part of the ion gel coating layer. Thus, a doped carbonization layer can be obtained outside the ion gel coating layer, which is beneficial to improving the conductivity of the composite material.
The preparation method of the composite material provided by the embodiment of the application has the advantages of simple flow, easiness in operation and suitability for large-scale production. In addition, in the composite material prepared by the preparation method, the coating layer containing the ionic gel has certain cohesiveness and good tensile property.
The third aspect of the embodiment of the application also provides an electrode plate, and the positive electrode plate comprises the composite material of the first aspect of the embodiment of the application.
The electrode plate can be a negative electrode plate or a positive electrode plate. Particularly, when the negative electrode plate contains the composite material with the inner core being the negative electrode active material, the negative electrode plate is not easy to be pulverized and fall off in the process of recycling the battery, and has good recycling performance.
The fourth aspect of the embodiment of the application also provides a secondary battery, which comprises the electrode plate of the third aspect of the embodiment of the application. The secondary battery may be a lithium secondary battery or other secondary battery or the like.
The secondary battery adopting the electrode plate containing the composite material has better cycle stability and better multiplying power performance, and can better meet the requirements of consumer electronic equipment, power vehicles and the like on long cycle life and high energy density of the secondary battery.
A fifth aspect of the embodiment of the present application provides an electronic device, which includes the secondary battery according to the fourth aspect of the present application. The secondary battery provided by the embodiment of the application is adopted to supply power, so that the physical examination and market competitiveness of the product can be improved.
Drawings
Fig. 1 is a schematic structural diagram of a composite material according to an embodiment of the present application.
Fig. 2 is a schematic structural view of a lithium secondary battery according to an embodiment of the present application.
Fig. 3 is a schematic structural diagram of an electronic device according to an embodiment of the present application.
Fig. 4 is a schematic structural diagram of another electronic device according to an embodiment of the present application.
FIG. 5 shows the surface microtopography and the elemental analysis of the spectrometer of the silicon oxide of example 1 of the present application before (a) and after (b) coating.
Detailed Description
The technical scheme of the application will be described below with reference to the accompanying drawings in the embodiments of the application.
Referring to fig. 1, a schematic structural diagram of a composite material according to an embodiment of the application is shown. The composite material 100 comprises an inner core 10 and a coating layer 20 coated on the inner core 10, wherein the inner core 10 comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent, the coating layer 20 comprises ionic gel, the ionic gel comprises a polymer and an ionic liquid, and the ionic liquid is dispersed in a three-dimensional network structure formed by the polymer.
The coating layer 20 in the application comprises ionic gel composed of matrix ionic liquid and polymer network framework, wherein the ionic liquid is uniformly dispersed in the polymer network structure, and the ionic gel is not subjected to macroscopic phase separation, is a solid soft material, has good toughness (such as good tensile property) and certain adhesiveness, can be firmly coated on the surface of the core material to form a stable coating layer, and can endow the coating layer 20 with certain deformability. When the core 10 is the anode active material, firstly, the coating layer 20 can expand/shrink along with the volume change of anode active material particles in the lithium deintercalation circulation process, and the coating layer 20 is not easy to damage/drop, so that the particle integrity of the core anode material in the battery circulation process is ensured, the circulation stability of the core anode material can be improved permanently, and the problem of circulation water jump of the core anode material is solved. Secondly, the adhesion of the ionic gel is favorable for the adhesion of the composite material 100 and the adhesive in the electrode pole piece, so that the adhesion firmness of the composite material 100 on the electrode pole piece is improved, and the failure caused by falling off from the pole piece in the volume expansion process is avoided. Thirdly, the ionic liquid with excellent ionic conductivity exists, so that the ionic conductivity of the coating layer 20 is higher, the interface impedance of the composite material 100 is lower, deep lithium intercalation is facilitated, the first effective capacity of the core 10 is improved, the conductivity of lithium ions on the surface of the composite material 100 is improved, the multiplying power performance of the core 10 is not affected, and the quick charge capacity of the material is improved. In addition, the ionic gel coating layer 20 is used as an artificial SEI layer (solid electrolyte interface, solid electrolyte interface layer) and can isolate the direct contact between the core material and the electrolyte, stabilize the interface and reduce side reactions with the electrolyte. Therefore, the ionic gel with good toughness, adhesiveness and high electrochemical performance is adopted as the coating layer, so that the volume expansion problem of the core can be solved and the cycle stability of the core can be improved while the multiplying power performance and capacity of the core material are not reduced.
When the core 10 is an active material of the positive electrode, the coating layer 20 has hydrophobicity, can play a role of isolating water and oxygen, can improve the stability of the positive electrode material of the core in air and water, prolongs the stable storage time, and prevents the structural change and performance degradation of the material caused by deliquescence and water absorption; in addition, the coating layer 20 helps to stabilize the slurry during stirring and pulping of the positive electrode slurry, and avoids problems such as slurry gelation and coating difficulty caused by easy water absorption and deterioration due to high residual alkali content on the surface of the positive electrode active material. For similar reasons in the upper stage, the coating layer 20 does not affect the rate performance and capacity performance of the core positive electrode material due to good ionic conductivity, and has a certain viscosity, so that the adhesion between the composite positive electrode material and the binder can be improved.
Similarly, when the core 10 is a lithium supplementing agent, the coating layer 20 also helps to improve the storage stability of the core and the stability of the slurry during the pulping process, and does not affect the lithium supplementing effect.
The coating layer 20 may cover the entire surface of the core 10 (as shown in fig. 1), or may cover only a part of the surface of the core 10, specifically, may cover a part of the surface of the core 10 continuously (e.g., a part of the surface of the core 10 has an island-shaped coating layer 20), or may cover the surface of the core 10 discontinuously, e.g., a plurality of island-shaped coatings at intervals.
In an embodiment of the present application, the negative electrode active material may include one or more of a carbon-based material, a silicon-based material, a phosphorus-based material, a tin-based material, a sulfur-based material, and the like. Among these, the negative electrode active material having a large volume expansion effect such as a silicon-based material, a phosphorus-based material, and a tin-based material is particularly required to be coated with the coating layer 20. The carbon-based material may include one or more of graphite (e.g., natural graphite, artificial graphite), soft carbon, hard carbon, anthracite, mesophase carbon microspheres, and the like; the silicon-based material may include one or more of elemental silicon, silicon-based alloys, silicon oxides (which may be represented by SiOx, 0< x <2, for example 0.9< x < 1.7), silicon-carbon composites, and the like; the phosphorus-based material may include one or more of elemental phosphorus (e.g., red phosphorus, black phosphorus, white phosphorus), phosphorus-carbon composite materials, and the like; the tin-based material may include one or more of elemental tin, tin alloys, tin oxides, and the like.
In the present application, the positive electrode active material may be selected according to active ions on which a specific secondary battery depends for energy storage. The active ions may include lithium ion, sodium ion, potassium ion, magnesium ion, aluminum ion, zinc ion, and the like. Wherein the positive electrode active material of the lithium secondary battery is lithium composite oxide including but not limited to lithium cobalt oxide (such as lithium cobaltate LiCoO 2 ) Lithium nickel oxide (e.g. lithium nickel oxide LiNiO 2 ) Lithium manganese oxide(e.g. lithium manganate LiMnO) 2 Lithium permanganate), lithium titanium oxide (such as lithium titanate), lithium iron phosphorus oxide (such as lithium iron phosphate, lithium manganese iron phosphate, etc.), lithium nickel cobalt oxide (such as lithium nickel cobalt oxide LiNi) a Co 1-a O 2 ) Lithium nickel manganese oxide (e.g. lithium nickel manganese oxide LiNi a Mn 1-a O 2 ) Nickel cobalt multi-element oxide (e.g. nickel cobalt lithium manganate LiNi a Co b Mn 1-a-b O 2 Lithium nickel cobalt aluminate LiNi a Co b Al 1-a-b O 2 Lithium nickel cobalt manganese aluminate (LiNi) a Co b Mn c Al 1-a-b- c O 2 ) One or more of the following. Wherein 0 is<a<1，0<b<1，0<c<1，0<1-a-b<1，0<1-a-b-c <1. For the sodium secondary battery, the positive electrode active material thereof may include one or more of sodium-containing composite oxide, prussian blue, prussian white, and the like. For a potassium secondary battery, the positive electrode active material may be a composite oxide containing potassium, and for a magnesium secondary battery, the positive electrode active material may be a composite oxide containing magnesium. The positive electrode active material may be undoped or doped-modified, and may be subjected to surface coating, pre-lithiation treatment, or the like. Wherein the particle size of the positive electrode active material may be in the range of 10nm to 100 μm.
For lithium secondary batteries, the lithium-supplementing agent may be a lithium-rich material, including but not limited to LiCoO 2 、Li 6 CoO 4 、 Li 2 MnO 3 、Li 2 CuO 2 、Li 2 NiO 2 、Li 5 FeO 4 、Li 2 CO 3 (lithium carbonate), li 2 C 2 O 4 (lithium oxalate), li 2 O (lithium oxide), li 2 O 2 (lithium peroxide), CH 3 And one or more of COOLi (lithium acetate). These lithium-supplementing agents may be undoped or doped modified, and may be subjected to surface coating, pre-lithiation treatment, or the like. The particle size of the lithium supplementing agent may be in the range of 10nm to 100 μm.
In an embodiment of the present application, the thickness of the cladding layer 20 is 5nm to 50nm. The thickness of the coating layer 20 can be adjusted according to the size of the core, and the coating layer 20 with a proper thickness can ensure that the coating layer can stably perform the function of the coating layer (such as providing buffering of the volume expansion of the core material, ensuring the storage or processing stability of the core, etc.), and meanwhile, the coating layer 20 has almost no electrochemical activity, and can not excessively increase the migration path of lithium ions in the coating layer due to the excessively thick thickness, reduce the gram capacity of the composite material, etc. Specifically, the thickness of the coating layer 20 may be specifically 8nm, 10nm, 15nm, 20nm, 22nm, 25nm, 30nm, 35nm, 40nm, 45nm, 48nm, or the like. In some embodiments, the thickness of the cladding layer 20 is 5nm to 30nm.
In the embodiment of the present application, the mass of the cladding layer 20 accounts for 0.5% -1% of the mass of the core 10. The coating 20 has a mass ratio within this range that facilitates the formation of a coating 20 of a suitable thickness and high coating integrity on the surface of the core material while avoiding excessive coating material from reducing the gram capacity of the composite 100. Specifically, the mass of the clad layer 20 may be 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, or 0.95% of the mass of the core 10, etc.
In the embodiment of the application, in the ionic gel, the mass ratio of the polymer is 5% -50%, and the mass ratio of the ionic liquid is 50% -95%. Wherein, the mass ratio of the ionic liquid in the ionic gel is controlled to be more than 50%, so that the ionic gel without obvious macroscopic phase separation is ensured to be formed; the mass ratio of the polymer in the ionic gel is below 50%, so that the strength of the ionic gel can be ensured not to be too high, the tensile property is good, the adhesive property is excellent, and the polymer can expand/shrink along with the ionic gel in the lithium intercalation process of the core negative electrode active material without damage and falling. In addition, unlike hydrogel with water as matrix or organic gel system with organic solvent as matrix, the ion gel has ionic liquid as matrix, so that the ion gel has high stability, and the ion gel coating is not easy to dissolve or volatilize, and can normally exert the function of the coating, and side reactions of the battery caused by the volatilization of the matrix in the running process of the battery are avoided. Illustratively, the ionic liquid may comprise 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. by mass of the ionic liquid in the ionic gel and the polymer may comprise 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% by mass of the ionic gel. In some embodiments, the ionic liquid comprises 60% to 75% by mass of the ionic gel. The mass ratio of the polymer in the ionic gel is 25% -40%.
In an embodiment of the application, the polymer comprises a polyacrylate structural unit represented by formula (I):
wherein R is 1 Selected from hydrogen, fluorine or methyl, R 2 Selected from the group consisting of hydrogen atoms, fluorine atoms, methyl groups, fluoromethyl groups, - (CH) 2 ) a -Z-, wherein a is an integer from 0 to 6, Z being selected from the group consisting of-COOH, -COOLi, -COONa, -COOK, - (CH) 2 CH 2 O) n H、 -(CH 2 CH 2 O) n CH 3 、-COOR 3 、-CONH 2 、-CONH(R 4 )、-CON(R 5 )(R 6 )；R 3 、R 4 、R 5 、R 6 Independently selected from C 1-6 N is independently selected from integers of 1-20 for each occurrence. In the structural unit represented by the formula (I), R 1 、 R 1 When the polymer is selected from the groups, the polymer with the structural unit shown in the formula (I) has larger polarity and can be successfully dissolved in the ionic liquid, so that the ionic gel without obvious macroscopic phase separation is obtained; in addition, R can be regulated 1 、R 1 And the ionic liquid is used for realizing the bonding performance of the ionic gel to different coated core materials.
The polymer may be a polymer comprising a structural unit represented by the formula (I) (in this case, the polymer ester is a homopolymer); or a structural unit comprising a plurality of different structures as shown in formula (I) (in this case, the polymer is a copolymer).
In the present application, the above polymer can be obtained by polymerizing a monomer corresponding to the polymer in the presence of an initiator. In embodiments of the present application, the number average molecular weight of the polymer is from 1kDa to 1000kDa (Da is a shorthand for daltons). The molecular weight of the polymer in the ionic gel is in the range, which is favorable for making the ionic gel layer have higher tensile strength and adhesiveness and ensuring good dispersibility of the polymer in the ionic liquid matrix.
In an embodiment of the application, in the ionic gel, the polymer can be crosslinked by physical action to form a three-dimensional network structure. Further, the three-dimensional network structure can be formed by crosslinking through chemical bond action. For example when R is as described above 2 Is- (CH) 2 ) a -COOH-、 -(CH 2 ) a -COOLi-、-(CH 2 ) a -COONa-、-(CH 2 ) a In COOK-, the polymer having the structural unit represented by the formula (I) may be chemically crosslinked in the presence of a crosslinking agent such as a polyepoxide, a polyol, a polyamine or the like to form a polymer network structure.
In an embodiment of the present application, the cations in the ionic liquid include one or more of nitrogen-containing heterocyclic cations, alkylammonium cations, and alkylphosphonium cations. Wherein the nitrogen-containing heterocyclic cations may include one or more of alkyl-substituted imidazole cations, alkyl-substituted pyrrole cations, alkyl-substituted pyridine cations, alkyl-substituted thiazole cations, and alkyl-substituted piperidine cations. When the cations of the ionic liquid are selected from the above ranges, each ionic liquid is in a liquid state at room temperature, the ionic conductivity is high, the chemical stability and the thermal stability are high, the electrochemical window is wide, and the stability in the electrode is good, so that the ionic liquid can exist stably on the surface of the core material, and the electrical performance of the core is not reduced. Wherein, the anions in the ionic liquid can comprise one or more of hexafluorophosphate, tetrafluoroborate, trifluoromethanesulfonyl, bis-cyanoimide, acetate, trifluoroacetate, inorganic acid radical and halogen ions. It will be appreciated that the ionic liquids in the ionic gel may be one or more (i.e. two or more) and that the anions and cations of each ionic liquid may be independently selected from the ranges set out above.
Wherein, in the azacyclic cations such as imidazole cations, pyrrole cations, pyridine cations, thiazole cations, piperidines, and the like, the alkyl group can replace a hydrogen atom on a ring hetero N atom. Further, alkyl groups may also replace hydrogen atoms on ring carbon atoms. The alkyl group may be a straight-chain or branched alkyl group having 1 to 6 carbon atoms. The alkyl ammonium cations may be specifically quaternary ammonium cations (i.e., nitrogen ions substituted with four alkyl groups), and the alkyl phosphonium cations may be specifically quaternary phosphonium salt cations.
The ionic conductivity of the coating 20 is higher due to the presence of ionic liquid in the ionic gel in the coating. In the embodiment of the present application, the ionic conductivity of the material of the coating layer 20 at room temperature is 10 -4 S·cm -1 The above. In some embodiments, the material of the coating layer 20 has an ionic conductivity of 10 at room temperature -4 S·cm -1 Up to 5X 10 -2 S·cm -1 Within a range of (2).
In the embodiment of the present application, the elongation at break of the clad layer 20 is 100% or more, and the breaking strength is in the range of 0.5MPa to 5 MPa. The elongation at break and the breaking strength are all indexes for measuring the tensile property of the material. The elongation at break is an index describing the plastic property of the material, and specifically refers to the ratio of the plastic elongation length delta L of the sample to the original length L of the sample when the sample is subjected to tensile fracture. The higher fracture elongation reflects the better toughness and excellent tensile property of the ionic gel coating layer. In some embodiments, the elongation at break of the coating 20 is in the range of 100% -500%, for example, 150%, 200%, 250%, 300%, 350%, 400%, 450%, or the like. Breaking strength is also known as "tensile strength" and refers to the ratio of the tensile force at which a material breaks to the cross-sectional area at which the material breaks. The higher breaking strength reflects the better toughness and excellent tensile properties of the ionic gel coating of the present application.
In the embodiment of the present application, the coating layer 20 is formed on the surface of the core material by a co-solvent evaporation method using a precursor solution containing a polymer and an ionic liquid. Compared with the ionic gel formed by in-situ crosslinking of the polymer monomer and the ionic liquid, the ionic gel provided by the embodiment of the application has higher toughness and no excessive rigidity.
In some embodiments of the present application, the coating layer 20 may further include one or more adjuvants selected from a conductive agent, a metal salt of an active metal ion, and a surfactant. Wherein the conductive agent is beneficial to improving the electronic conductivity of the coating layer 20, the metal salt is beneficial to improving the ionic conductivity of the coating layer 20, and the surfactant is beneficial to improving the surface energy of the coating layer, so that the binding force between the coating layer material and the core material particles is increased. Wherein the conductive agent may include one or more of conductive carbon black, carbon nanotubes, graphene, graphite, amorphous carbon, and the like. The metal ion of the metal salt may include one or more of lithium ion, sodium ion, potassium ion, magnesium ion, etc., and the anion may include one or more of hexafluorophosphate, tetrafluoroborate, trifluoromethanesulfonamide, bistrifluoromethanesulfonimide, dicyanoimide, acetate, trifluoroacetate, inorganic acid, halogen ion, etc. The surfactant may include one or more of amphiphilic small organic molecules, amphiphilic nonionic polymers, amphiphilic ionic polymers, and the like. The types and contents of the conductive agent, metal salt, and surfactant may be adjusted according to the specific composition system and application scenario of the composite material 100.
In some embodiments of the application, the coating 20 has a carbonization layer containing doping elements derived from the ionic liquid. In the present application, the carbonized layer may be obtained by carbonizing a part of the clad layer 20, for example, by calcining at 450 to 650 ℃. The doping element can be one or more of N, S, P and halogen elements.
Compared with the anode active material without the coating layer, the anode active material and the lithium supplementing agent, the composite material with the ionic gel coating layer provided by the embodiment of the application has better electrical property, mechanical property, good stability and the like.
The embodiment of the application also provides a preparation method of the composite material, which comprises the following steps:
s01, dispersing a polymer and an ionic liquid into a solvent to obtain an ionic gel precursor solution;
s02, mixing the core material with the ionic gel precursor solution to obtain a mixed material; wherein the core material comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent;
s03, removing the solvent in the mixed material, and forming a coating layer containing ionic gel on the surface of the core material in the process of removing the solvent to obtain the composite material.
The selection range of the ionic liquid and the polymer can be referred to in the previous description of the application, and the description is omitted here. According to the application, the polymer is directly adopted in the preparation precursor solution instead of the polymer monomer, so that the situation that the polymer monomer and the ionic liquid are in-situ crosslinked to form the ionic gel is over-strong, the cohesiveness is insufficient, the ionic gel cannot have better tensile fatigue resistance, and further, the situation that the anode active material coated by the ionic gel cannot maintain good coating layer integrity in multiple circulating volume changes is avoided; in addition, the precursor prepared from the polymer and the ionic liquid is favorable for the dispersion uniformity of the polymer in the ion gel coating layer formed later.
In the step S01, the mass ratio of the polymer to the ionic liquid is 1: (1-19). The mass ratio of the two is within the range, so that the ionic gel without obvious macroscopic phase separation can be formed in the subsequent solvent removal process, and the tensile property of the ionic gel can be ensured. In some embodiments of the application, the mass ratio of polymer to ionic liquid is 1: (1.5-3). In this case, the ionic gel formed by the two can better give consideration to both good tensile property and adhesive property.
In an embodiment of the present application, in step S01, the solvent used should be capable of dissolving the polymer and the ionic liquid, wherein the solvent may include, but is not limited to, one or more of methanol, ethanol, dichloromethane, chloroform, acetone, tetrahydrofuran, dioxane, toluene, chlorobenzene, N-Dimethylformamide (DMF), N-methylpyrrolidone (NMP), and Dimethylsulfoxide (DMSO). In some embodiments, the mass ratio of the sum of the mass of polymer and ionic liquid to the mass of solvent in the ionic gel precursor solution is 1: (5-20). Thus, the polymer and the ionic liquid can be fully dissolved in the solvent. Optionally, in step S01, the polymer and the ionic liquid are dissolved in the solvent, and the stirring time may be 5-12 hours; the stirring speed during stirring may be 300-500rpm.
In some embodiments of the present application, the ionic gel precursor solution of step S01 may further contain an auxiliary agent, wherein the auxiliary agent includes, but is not limited to, one or more of the aforementioned conductive agents, metal salts of active metal ions, surfactants, and the like. Wherein the mass ratio of the sum of the mass of the polymer and the mass of the ionic liquid to the mass of the auxiliary agent can be 1: (0.1-0.5).
In step S02, the core material is typically a negative electrode active material, a positive electrode active material, a lithium supplementing agent, or the like. And mixing the core material with the ionic gel precursor solution to enable the surface of the core material to adsorb the ionic gel precursor solution. Based on the fluidity of the precursor solution, the precursor solution can permeate into the tiny gaps on the surface of the core material, and the coating layer formed after the treatment in the step S03 can improve the interface performance of the core material, increase the active sites of the core material and improve the specific capacity of the core material.
In some embodiments of the application, the mass ratio of the sum of the mass of polymer and ionic liquid to the mass of core material may be in the range of 1: (100-200). Thus, after the treatment of the step S03, the ionic gel coating layer with proper thickness and higher coating integrity is formed on the surface of the core material, and the gram capacity of the whole composite material is prevented from being reduced.
In step S02, the mixing manner of the core material and the ionic gel precursor solution may be a mechanical stirring method, a high-energy ball milling method, or a mechanical fusion method. In some embodiments, the mixing is accomplished using a mechanical agitation process, wherein the agitation may be performed at 20-60 ℃; the stirring time may be 3h-15h. To avoid the solid core material sinking to the bottom of the vessel during stirring, the stirring speed can be controlled in the range of 300-500 rpm. The core material may be directly mixed with the ion gel precursor solution in the form of a powder material, or may be added in the form of a dispersion formed by the ion gel precursor solution and a solvent. In some embodiments of the application, the core material is first mixed with the solvent under stirring (for example, for a period of 1-2 hours) to obtain a dispersion of the core material; then stirring and mixing with the ionic gel precursor solution (stirring time is 2-12h for example). In some embodiments, the above-described adjuvants such as conductive agents, metal salts, surfactants, and the like may also be added with the core material, for example, the adjuvants may be added to the dispersion of the core material.
In step S03, the solvent may be removed at a temperature such that the solvent volatilizes. In the process of volatilizing the solvent, the ionic liquid and the polymer spontaneously form homogeneous ionic gel and are coated on the surface of the core material. The temperature for removing the solvent can be determined according to the volatilization temperature of the specific solvent. The solvent removal mode can comprise rotary evaporator spin drying, water bath stirring drying, oven drying and the like. These solvent removal means ensure that the solvent in the mixture is largely removed, even completely removed, to give a substantially dry powder sample.
In some embodiments of the application, after removing the solvent, further comprising: and (3) carrying out heat treatment on the solid material obtained after the solvent is removed at the temperature of 50-80 ℃. The heat treatment can enhance the fluidity of the ionic gel on the surface of the core material and promote the coating uniformity of the coating layer. The heat treatment time may be 8 to 24 hours. Wherein, the heating treatment can be vacuum drying in a vacuum oven. In some embodiments of the present application, the solvent mixture may be spin-dried in a rotary evaporator to obtain a high-dryness composite material.
In some embodiments of the present application, after the heat treatment is completed, the resulting crude composite material may be subjected to a sieving treatment to obtain a composite material of desired particle size. Considering the thinner thickness of the ion gel coating layer in the application, the size of the screened composite material is basically equivalent to the size of the adopted micron-sized core material raw material at the level of 5-50 nm.
In some embodiments of the present application, after step S03, the composite material obtained in step S03 may be calcined at a high temperature, so as to carbonize a part of the ion gel coating layer. At this time, the obtained composite material includes an inner core, an ion gel coating layer surrounding the inner core, and a carbonized layer (i.e., an inorganic carbon coating layer) containing a doping element surrounding the ion gel coating layer.
According to the preparation method of the composite material, the precursor solution of the polymer and the ionic liquid is mixed with the core material, and then the solvent is evaporated, so that a stable ionic gel coating layer can be formed on the surface of the core material, the coating layer has strong binding force with the core material and high toughness, the interface performance of the core material can be well improved, for example, the volume expansion problem of the core anode active material can be improved, the water-oxygen stability of the core anode active material or the core lithium supplementing agent can be improved, and the like.
The preparation method of the composite material has the advantages of simple process, easy operation, suitability for large-scale production, high structural stability and good electrochemical performance.
The embodiment of the application also provides an electrode plate for a battery, which contains the composite material. The electrode plate can be a negative electrode plate or a positive electrode plate.
In an embodiment of the present application, the negative electrode sheet includes the negative electrode active material having the ionic gel coating layer on the surface (i.e., the composite material 100 in which the core 10 is the negative electrode active material) described above, and may be referred to as a "composite negative electrode material". In one embodiment, the negative electrode tab comprises a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector, the negative electrode material layer comprising the aforementioned composite negative electrode material, a binder, and optionally a conductive agent. At this time, the negative electrode plate is not easy to be pulverized and fall off in the battery charging and discharging cycle process.
In an embodiment of the present application, the positive electrode sheet includes the positive electrode active material having the ionic gel coating layer on the surface (i.e., the composite material 100 in which the core 10 is the positive electrode active material may be simply referred to as "composite positive electrode material"), and/or the lithium supplementing agent having the ionic gel coating layer on the surface (i.e., the composite material 100 in which the core 10 is the lithium supplementing agent may be referred to as "composite lithium supplementing agent").
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on the positive electrode current collector, the positive electrode material layer including the aforementioned composite positive electrode material, a binder, and a conductive agent. In some embodiments, the positive electrode material layer may further contain the aforementioned composite lithium-supplementing agent. In other embodiments, the side of the positive electrode material layer facing away from the positive electrode current collector further has an additive layer containing the aforementioned composite lithium-supplementing agent, binder, and conductive agent. Since the surface of the positive electrode active material or the lithium supplementing agent is provided with the ionic gel coating layer, the slurry is not easy to gel in the process of preparing positive electrode slurry for the positive electrode material layer and additive slurry for the additive layer, and the coating quality is less affected. In addition, the substrates of the coating layers are not volatile ionic liquid, but not volatile water or organic solvent, so that the integrity of the coating layers is not damaged due to the volatilization of the substrates in the drying process of the pole piece, and side reactions caused by water and the like are reduced in the operation process of the battery.
The binder and the conductive agent are all conventional choices in the field of batteries. The binder may specifically include, but is not limited to, one or more of Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate, polyacrylamide (PAM), polyimide (PI), and the like. The conductive agent may specifically include, but is not limited to, one or more of acetylene black, ketjen black, provider P conductive carbon black, graphite, graphene, carbon nanotubes, carbon fibers, amorphous carbon, and the like. The negative electrode current collector comprises, but is not limited to, a metal foil, an alloy foil or a metal plating film, and the surface of the negative electrode current collector can be etched or roughened to form a secondary structure so as to be in effective contact with the negative electrode material layer. Exemplary metal foils may be copper foil, carbon coated copper foil, or copper coated film, and exemplary alloy foils may be stainless steel foil, copper alloy foil, or the like. Similarly, positive electrode current collectors include, but are not limited to, metal foils, alloy foils, or metallized films, the surfaces of which may be etched or roughened to form secondary structures that facilitate effective contact with the positive electrode material layer. Exemplary metal foils may be aluminum foil, carbon coated aluminum foil, or aluminized film, and exemplary alloy foils may be stainless steel foil, aluminum alloy foil, or carbon coated stainless steel foil.
Referring to fig. 2, an embodiment of the present application also provides a secondary battery 200 including the above electrode tab.
The secondary battery 200 may be a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, or the like. In one embodiment, the secondary battery 200 is a lithium secondary battery. The lithium secondary battery includes a positive electrode 201, a negative electrode 202, a separator 203 and an electrolyte 204 provided between the positive electrode 201 and the negative electrode 202, and corresponding communication auxiliaries and circuits. The positive electrode 201 and/or the negative electrode 202 according to the embodiment of the present application include the positive electrode sheet according to the embodiment of the present application.
In the present application, the separator 203 may be a polymer separator, a nonwoven fabric, etc., including but not limited to a single-layer PP (polypropylene) film, a single-layer PE (polyethylene) film, a double-layer PP/PE, a double-layer PP/PP, a triple-layer PP/PE/PP, etc. Electrolyte 204 includes a reactive ion salt (particularly a lithium salt) and an organic solvent that may include, but is not limited to, one or more of a carbonate solvent, a carboxylate solvent, an ether solvent.
In the charging process of the lithium secondary battery, under the action of an external circuit, lithium ions are separated from the positive electrode 201 and migrate to the negative electrode 202 through the electrolyte 204 and the diaphragm 203, meanwhile, electrons flow from the positive electrode to the negative electrode through the external circuit, and electric energy is stored; during discharging, lithium ions are separated from the negative electrode 202, returned to the positive electrode 201 through the electrolyte 204 and the diaphragm 203, and corresponding electrons migrate from the negative electrode to the positive electrode through an external circuit, so that electric energy is released to the outside.
The capacity of the positive and negative electrodes is critical to the improvement of the energy density of the entire cell of the secondary battery. The negative electrode 202 of the lithium secondary battery 200 of the present application contains the negative electrode active material with the ionic gel coating layer on the surface (i.e., the composite material 100 with the core 10 being the negative electrode active material), when the negative electrode active material is a theoretical capacity-high (for example, when the negative electrode active material is a silicon-based or phosphorus-based negative electrode active material), the composite material of the present embodiment can improve the cycle stability, reduce the volume expansion, and improve the rate capability while maintaining the high capacity of the negative electrode material, thereby being beneficial to improving the capacity, the service life, the safety and the quick charge capability of the current lithium battery. In addition, when the positive electrode 201 of the lithium secondary battery 200 contains the positive electrode active material or the lithium supplementing agent with the ionic gel coating layer on the surface, the slurry in the pulping process is good in stability and difficult to gel in the preparation process of the positive electrode plate of the battery, and the coating layer can reduce the structural damage of the positive electrode active material or the lithium supplementing agent caused by trace moisture and the like in the electrolyte in the operation process of the battery, so that the cycle life of the battery is ensured.
The secondary battery provided by the embodiment of the application can be used for terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers, digital cameras, other wearable or movable electronic equipment, unmanned aerial vehicles, electric automobiles, energy storage equipment and other products, so as to improve the competitiveness of the products.
The embodiment of the application also provides electronic equipment comprising the secondary battery. The electronic device may be a product including various consumer electronics such as a cell phone, tablet computer, notebook computer, mobile power supply, portable, and other wearable or removable electronic devices, televisions, video disc player, video recorder, camcorder, radio recorder, audio unit, electric singer, laser player, home office equipment, home electronic health care equipment, and may also be an automobile, energy storage device, etc.
In some embodiments, referring to fig. 3, an embodiment of the present application provides an electronic device 300, which includes a housing 301, and electronic components (not shown in fig. 3) and a battery 302 that are accommodated in the housing 301, wherein the battery 302 supplies power to the electronic device 300, and the battery 302 includes the lithium secondary battery 200 described above in the embodiment of the present application. In some embodiments, the housing 301 may include a front cover assembled at the front side of the terminal and a rear case assembled at the rear side, and the battery 302 may be fixed inside the rear case.
In other embodiments, referring to fig. 4, an embodiment of the present application provides an electronic device 400 that may be a variety of mobile devices for loading, transporting, assembling, disassembling, security, etc., such as various forms of vehicles. Specifically, the electronic device 400 may include a vehicle body 401, a moving component 402, and a driving component, where the driving component includes a motor 403 and a battery system 404, and the battery system 404 includes the secondary battery 200 provided in the embodiment of the present application. Wherein the moving assembly 402 may be a wheel. The battery system 404 may be a battery pack including the above-described secondary battery 200, which is accommodated at a bottom of a body of the vehicle and electrically connected to the motor 403, and which may supply power to the motor 403, and the motor 403 supplies power to drive the moving assembly 402 of the electronic device 400 to move.
The following examples are provided to further illustrate embodiments of the application.
Example 1 ion gel coated negative electrode active Material
(1) 30mg of a poly (lithium acrylate-ethyl acrylate) copolymer having a number average molecular weight of 100kDa (the copolymer also contains structural units60mg of ionic liquid (specifically 1-ethyl-3-methylimidazole bis (trifluoromethanesulfonyl) imide salt) is added into 1g of methanol, and the polymer and the ionic liquid are completely dissolved at the temperature of 30 ℃ and the rotating speed of 300rpm for 6 hours, so that an ionic gel precursor solution is obtained;
(2) 10g of a negative electrode active material powder (specifically, silicon oxide having a carbon coating layer on the surface thereof, siOx@C, particle diameter of about 5 μm) was added to 30g of methanol, and the mixture was rotated at 300rpm for 1 hour at 30℃to obtain a dispersion of the silicon oxide material; adding the precursor solution in the step (1) into the dispersion liquid of the silicon oxygen material in a stirring state, and obtaining a mixed material at the temperature of 30 ℃ and the rotating speed of 300rpm for 6 hours;
(3) The solvent methanol in the mixture is removed by rotary evaporation (under the reduced pressure of 40 ℃), and the obtained powder sample is placed in a vacuum drying oven for drying at 50 ℃ for 24 hours, so that the composite anode material, namely the silicon oxide with the ion gel coating layer on the surface, is obtained. The ionic gel comprises a poly (acrylic acid-lithium acrylate-ethyl acrylate) copolymer and 1-ethyl-3-methylimidazole bistrifluoromethylsulfonylimine salt dispersed in the three-dimensional network structure of the copolymer.
Fig. 5 shows the surface microtopography and the elemental analysis results of the spectrometer (Energy Dispersive Spectroscopy, EDS) of the silicon oxide of example 1 of the present application before (a) and after (b) coating. In contrast to the silicon oxide shown in column (a) of fig. 5, which was not coated with the ionic gel, it can be seen that the gel-like coating was present on the surface of the silicon oxide after the treatment by the above-described method of example 1 of the present application. The surface EDS element analysis characterization also shows that after coating, the content of C, O element in the obtained composite material is obviously improved, and the content of Si is reduced, which indicates that a new organic matter coating layer exists on the surface of the material.
In the composite anode material obtained in example 1, the mass ratio of the ionic liquid in the ionic gel coating layer was 66.7%, and the mass ratio of the three-dimensional network structure formed by the polymer was about 33.3%. The thickness of the coating layer is about 6nm, and the ionic conductivity of the coating layer at room temperature is about 5×10 -3 S·cm -1 The elongation at break of the coating layer was 470% and the breaking strength was 2.5 MPa.
Example 2
The composite anode material of example 2 differs from example 1 in that: and (3) adding a conductive agent, namely single-arm carbon nano tubes, into the dispersion liquid of the silicon oxygen material in the step (2).
Comparative example 1
The negative electrode active material was directly siox@c, which was used as a core material in example 1, without surface modification.
The composite anode material obtained in the examples 1 and 2 and SiOx@C of the comparative example 1 are respectively mixed with a binder (specifically a commercial polyacrylic acid aqueous solution) and a conductive agent (specifically Super P conductive carbon black) according to the mass ratio of 75:15:10, diluted with water and fully stirred to obtain anode slurry; coating the negative electrode slurry on a negative electrode current collector (specifically copper foil), vacuum drying, rolling and separatingAnd cutting to obtain the negative electrode plate. The metal lithium sheet is used as a counter electrode, and the negative electrode sheet, the commercial PE diaphragm and 1mol/L LiPF are used as the counter electrode 6 And (2) electrolyte (EC+DEC) (volume ratio 1:1), and assembling the electrolyte into the 2032 type button cell in a glove box protected by argon.
In order to strongly support the beneficial effects of the examples of the present application, the button cells prepared from the composite anode materials of examples 1-2 and comparative example 1 were subjected to electrochemical performance tests as shown in table 1, wherein the button cells were subjected to charge and discharge tests at a test temperature 2525 ℃ and a charge and discharge rate of 0.05C/0.02C within a voltage interval of 0.05V to 1.5V.
TABLE 1 Battery Performance test results for different samples
As can be seen from table 1, after the commercial anode active material siox@c is coated with the ionic gel layer according to the embodiment of the application, the cycle stability of the lithium button cell prepared by using the commercial anode active material siox@c is obviously improved, the expansion rate of the anode piece is greatly reduced, and the first lithium removal capacity of the cell is also improved to a certain extent.
Example 3
The composite anode material of example 3 differs from example 1 in that: the solvent of example 1 was replaced with acetone, and the poly (lithium acrylate-ethyl acrylate) copolymer of example 1 was replaced with a poly (vinylidene fluoride-co-hexafluoropropylene) copolymer having a number average molecular weight of 450kDa, which polymer contained both structural unitsAnd
specifically, the preparation method of the composite anode material of example 3 includes the following steps:
(1) 30mg of poly (vinylidene fluoride-co-hexafluoropropylene) copolymer with the number average molecular weight of 450kDa and 60mg of ionic liquid (specifically 1-ethyl-3-methylimidazole bistrifluoromethanesulfonimide salt) are added into 1g of acetone, and the polymer and the ionic liquid are completely dissolved at the temperature of 30 ℃ for 6 hours at the rotating speed of 300rpm, so as to obtain an ionic gel precursor solution;
(2) 10g of a negative electrode active material powder (specifically, a commercial silicone material) was added to 30g of acetone, and the mixture was rotated at 300rpm at 30℃for 1 hour to obtain a dispersion of the silicone material; adding the precursor solution in the step (1) into the dispersion liquid of the silicon oxide material in a stirring state, and obtaining a mixed material at the temperature of 30 ℃ and the rotating speed of 300rpm for 6 hours;
(3) And removing the solvent acetone in the mixed material by rotary evaporation (at the reduced pressure of 40 ℃), and placing the obtained powder sample in a vacuum drying oven for drying at 50 ℃ for 24 hours to obtain the composite anode material, namely the silicon oxide with the ion gel coating layer on the surface. The ionic gel comprises a poly (vinylidene fluoride-co-hexafluoropropylene) copolymer and 1-ethyl-3-methylimidazole bistrifluoromethanesulfonimide salt dispersed in the three-dimensional network structure of the copolymer.
Wherein the ionic gel coating layer in the composite anode material obtained in example 3 has an ionic conductivity of about 3×10 at room temperature -3 S·cm -1 The elongation at break of the coating layer was 200% and the breaking strength was 2MPa.
Example 4
The preparation method of the composite anode material provided in example 4 is different from that of example 1 in that: and (3) adding a trifunctional aziridine crosslinking agent into the dispersion liquid of the silicon oxygen material in the step (2).
Wherein the ionic gel coating layer in the composite anode material obtained in example 4 has an ionic conductivity of about 4×10 at room temperature -3 S·cm -1 The elongation at break of the coating layer was 200% and the breaking strength was 4.5MPa.
Compared with the example 1, under the same condition, after the cross-linking agent auxiliary agent is introduced, the breaking strength of the ion gel coating layer is improved to a certain extent.
Example 5
The preparation method of the composite anode material provided in example 5 is different from that of example 1 in that: the ionic liquid is specifically 1-ethyl-3-methylimidazole hexafluorophosphate.
Wherein the ionic gel coating layer in the composite anode material obtained in example 5 has an ionic conductivity of about 4.2X10 at room temperature -3 S·cm -1 The elongation at break of the coating layer was 450%, and the breaking strength was 2.5MPa.
Example 6
The preparation method of the composite anode material provided in example 6 is different from that of example 1 in that: the ionic liquid used was in particular N-butyl-N-methylpyrrolidine bis (trifluoromethanesulfonyl) imide salt (CAS number 223437-11-4).
Wherein the ionic gel coating layer in the composite anode material obtained in example 6 has an ionic conductivity of about 4.5X10 at room temperature -3 S·cm -1 The elongation at break of the coating layer was 400% and the breaking strength was 3MPa.
Example 7
The preparation method of the composite anode material is different from that of the embodiment 1 in that: the amount of poly (acrylic acid-lithium acrylate-ethyl acrylate) copolymer of example 1 was modified from 30mg to 45mg and the amount of ionic liquid was modified from 60mg to 45mg.
Wherein the thickness of the ion gel coating layer in the composite anode material obtained in example 7 was about 5nm, and the ion conductivity of the coating layer at room temperature was about 2X 10 -3 S·cm -1 The elongation at break of the coating layer was 200% and the breaking strength was 4MPa.
Example 8
The preparation method of the composite anode material is different from that of the embodiment 1 in that: the amount of poly (acrylic acid-lithium acrylate-ethyl acrylate) copolymer of example 1 was modified from 30mg to 4.5mg and the amount of ionic liquid was modified from 60mg to 85.5mg.
Wherein the thickness of the ion gel coating layer in the composite anode material obtained in example 8 was about 5nm, and the ion conductivity of the coating layer at room temperature was about 8X 10 -3 S·cm -1 The elongation at break of the coating layer was 1000%,the breaking strength was 1MPa.
From examples 7 to 8 and example 1, it can be seen that when the total mass of the ionic gel is unchanged and the ionic liquid is relatively large, the ionic conductivity of the ionic gel coating layer is relatively high, the breaking elongation is large, and the breaking strength is reduced.
Example 9
The preparation method of the composite anode material is different from that of the embodiment 1 in that: the amount of poly (acrylic acid-lithium acrylate-ethyl acrylate) copolymer of example 1 was increased from 30mg to 40mg.
In the composite anode material obtained in example 9, the thickness of the ion gel coating layer was about 8nm, the mass of the coating layer was 1% of the mass of the core, and the ion conductivity of the coating layer at room temperature was about 4X 10 -3 S·cm -1 The elongation at break of the coating layer was 200% and the breaking strength was 5MPa.
Example 10
The preparation method of the composite anode material is different from that of the embodiment 1 in that: the amount of poly (acrylic acid-lithium acrylate-ethyl acrylate) copolymer in example 1 was increased from 30mg to 120mg, the amount of 1-ethyl-3-methylimidazolium bistrifluoromethylsulfonylimide salt was increased from 60mg to 240mg, and the corresponding amount of organic solvent methanol was also increased four times, keeping the quality of the active material unchanged.
In the composite anode material obtained in example 10, the thickness of the ion gel coating layer was about 20nm, and the ion conductivity of the coating layer at room temperature was about 5×10 -3 S·cm -1 The elongation at break of the coating layer was 470% and the breaking strength was 2.5MPa.
Compared with example 1, the mass ratio of the coating layer in the whole composite anode material in example 10 is improved, so that the stability of the material is further improved, the first coulombic efficiency is improved, but the capacity of the material is reduced to a certain extent due to the increase of inactive components. The composite anode material of example 10 was fabricated into a button cell in the manner of example 1, and the initial coulombic efficiency was 88% (86% in example 1), wherein the initial lithium intercalation capacity was 1448.1mAh/g and the initial lithium deintercalation capacity was 1274.3mAh/g.
Example 11
The preparation method of the composite anode material is different from that of the embodiment 1 in that: in step (3), after vacuum drying, the obtained solid powder was further subjected to high temperature calcination at 550 ℃ for 3 hours to carbonize a part of the ion gel coating layer.
The composite anode material obtained in example 11 further had an inorganic carbon coating layer (containing F, N, S doping element) having a thickness of about 1nm outside the ion gel coating layer. The presence of the carbon-doped coating layer is beneficial to improving the conductivity of the composite anode material, and further the rate performance of a battery prepared from the composite anode material is improved.
Example 12
Example 12 provides a composite positive electrode material, which is prepared by a method different from that of example 1 in that: the negative electrode active material-silicon oxide in example 1 was replaced with a high-nickel ternary positive electrode active material (its structural formula is nickel cobalt lithium manganate LiNi 0.83 Co 0.12 Mn 0.05 O 2 Particle size of about 4.3 μm).
Wherein, in the composite positive electrode material obtained in example 12, the thickness of the ion gel coating layer was about 8nm, the elongation at break of the coating layer was 470%, and the breaking strength was 2.5MPa.
Compared with uncoated nickel cobalt lithium manganate, the core-shell composite anode material provided by the embodiment 12 of the application can be stored for 30 days under the environment humidity of 25%, and deliquescence and water absorption can not occur; the electrochemical performance of the pure high nickel cobalt manganese ternary material is reduced due to deliquescence after being stored for more than one day under the humidity, and the gelation phenomenon is easy to occur when the material is used for preparation. This indicates that the ionic gel coating layer can improve the water-oxygen stability of the core positive electrode active material. In addition, when the composite positive electrode material, the binder, the conductive agent and the water are prepared into positive electrode slurry, the slurry gelation phenomenon can not occur due to the existence of the ion gel coating layer on the surface of the inner core in the process of pulping and stirring.
The foregoing description of several exemplary embodiments of the application has been presented only, and is thus not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (15)

1. A composite material, characterized in that the composite material comprises a core and a coating layer coated on the core, wherein the core comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent, the coating layer comprises ionic gel, the ionic gel comprises a polymer and an ionic liquid, and the ionic liquid is dispersed in a three-dimensional network structure formed by the polymer.
2. The composite material of claim 1, wherein the coating has a thickness of 5nm to 50nm.
3. The composite material according to claim 1 or 2, wherein the ionic gel has a mass ratio of 5% to 50% of the polymer and a mass ratio of 50% to 95% of the ionic liquid.
4. A composite material according to any one of claims 1 to 3, wherein the polymer comprises structural units of formula (i):
wherein R is 1 Selected from hydrogen, fluorine or methyl, R 2 Selected from the group consisting of hydrogen atoms, fluorine atoms, methyl groups, fluoromethyl groups, - (CH) 2 ) a -Z-, wherein a is an integer from 0 to 6, Z being selected from the group consisting of-COOH, -COOLi, -COONa, -COOK, - (CH) 2 CH 2 O) n H、-(CH 2 CH 2 O) n CH 3 、-COOR 3 、-CONH 2 、-CONH(R 4 )、-CON(R 5 )(R 6 )；R 3 、R 4 、R 5 、R 6 Independently selected from C 1-6 N is independently selected from integers of 1-20 for each occurrence.
5. The composite material of any one of claims 1-4, wherein the polymer has a number average molecular weight of 1kDa to 1000kDa.
6. The composite of any of claims 1-5, wherein the cations in the ionic liquid comprise one or more of alkyl substituted imidazole cations, alkyl substituted pyrrole cations, alkyl substituted pyridine cations, alkyl substituted thiazole cations, alkyl substituted piperidine cations, alkyl ammonium cations, alkyl phosphonium cations.
7. The composite material of any one of claims 1-6, wherein the coating layer has an ionic conductivity of 10 at room temperature -4 S·cm -1 The above.
8. The composite material of any one of claims 1-7, wherein the coating has an elongation at break of 100% or more and a strength at break in the range of 0.5MPa to 5 MPa.
9. The composite material of any one of claims 1-8, wherein the coating further comprises one or more of a conductive agent, a metal salt of an active metal ion, and a surfactant.
10. The composite material of any one of claims 1-9, wherein the cladding layer is further provided with a carbonization layer comprising a doping element, wherein the doping element is derived from the ionic liquid.
11. A method of preparing a composite material, comprising the steps of:
dispersing a polymer and an ionic liquid into a solvent to obtain an ionic gel precursor solution;
mixing the core material with the ionic gel precursor solution to obtain a mixed material; wherein the core material comprises a negative electrode active material, a positive electrode active material or a lithium supplementing agent;
and removing the solvent in the mixed material, and forming a coating layer containing ionic gel on the surface of the core material in the removal process of the solvent to obtain the composite material.
12. The method of preparing as claimed in claim 11, further comprising, after removing the solvent:
and (3) carrying out heat treatment on the solid material obtained after the solvent is removed at the temperature of 50-80 ℃.
13. An electrode sheet comprising the composite material of any one of claims 1-10.
14. A secondary battery comprising the electrode tab of claim 13.
15. An electronic device comprising the secondary battery according to claim 14.
CN202210468809.1A 2022-04-29 2022-04-29 Composite material, preparation method and application thereof Pending CN117012910A (en)

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KR101545432B1 (en) * 2013-01-28 2015-08-18 주식회사 엘지화학 Lithium secondary battery
KR102268076B1 (en) * 2017-06-09 2021-06-23 주식회사 엘지에너지솔루션 Positive electrode for secondary battery, method for preparing the same, and lithium secondary battery comprising the same
CN109994710B (en) * 2017-12-29 2022-07-12 宁德时代新能源科技股份有限公司 Composite negative electrode material, preparation method thereof, negative electrode plate and battery
CN113380990A (en) * 2020-02-25 2021-09-10 郑州宇通集团有限公司 Lithium ion battery composite positive electrode material, preparation method thereof and lithium ion battery
CN111933940B (en) * 2020-07-31 2021-12-31 四川大学 Lithium battery composite electrode piece and preparation method and application thereof
CN114335705B (en) * 2020-09-28 2024-05-03 中国科学院苏州纳米技术与纳米仿生研究所 Integrated all-solid-state battery and preparation method thereof
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CN117352954A (en) * 2023-12-06 2024-01-05 天津力神电池股份有限公司 Sodium-supplementing electrolyte diaphragm, preparation method and battery
CN117352954B (en) * 2023-12-06 2024-04-19 天津力神电池股份有限公司 Sodium-supplementing electrolyte diaphragm, preparation method and battery

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