CN116525823A - Positive electrode lithium supplementing material and preparation method and application thereof - Google Patents
Positive electrode lithium supplementing material and preparation method and application thereof Download PDFInfo
- Publication number
- CN116525823A CN116525823A CN202211685749.5A CN202211685749A CN116525823A CN 116525823 A CN116525823 A CN 116525823A CN 202211685749 A CN202211685749 A CN 202211685749A CN 116525823 A CN116525823 A CN 116525823A
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- Prior art keywords
- lithium
- positive electrode
- shell
- shell layer
- reinforcing particles
- Prior art date
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 186
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 186
- 239000000463 material Substances 0.000 title claims abstract description 138
- 230000001502 supplementing effect Effects 0.000 title claims abstract description 61
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000002245 particle Substances 0.000 claims abstract description 148
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 115
- 239000011162 core material Substances 0.000 claims abstract description 86
- 239000003792 electrolyte Substances 0.000 claims abstract description 20
- 239000011257 shell material Substances 0.000 claims description 235
- 239000010410 layer Substances 0.000 claims description 216
- 238000000034 method Methods 0.000 claims description 36
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 22
- 239000003575 carbonaceous material Substances 0.000 claims description 18
- 239000011247 coating layer Substances 0.000 claims description 17
- 239000007774 positive electrode material Substances 0.000 claims description 17
- 239000004005 microsphere Substances 0.000 claims description 15
- 238000005245 sintering Methods 0.000 claims description 14
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 claims description 13
- 238000005538 encapsulation Methods 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 10
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- 239000000377 silicon dioxide Substances 0.000 claims description 7
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 claims description 6
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Chemical compound [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 claims description 6
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 18
- 229910001416 lithium ion Inorganic materials 0.000 description 18
- 239000000243 solution Substances 0.000 description 16
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- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
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Classifications
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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
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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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
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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
- H01M4/624—Electric conductive fillers
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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
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The application discloses a positive electrode lithium supplementing material and a preparation method and application thereof, wherein the positive electrode lithium supplementing material comprises a lithium-rich core material and a first shell layer, the first shell layer is arranged on the outer surface of the lithium-rich core material, and reinforcing particles are embedded on the surface and/or the inside of the first shell layer. The application positive pole benefit lithium material has the first shell that contains reinforcing particle on the lithium rich material kernel cladding, and wherein reinforcing particle's setting can promote the stability of first shell on the one hand, prevents to mend lithium material and electrolyte direct contact because of the cladding is easily destroyed and lead to, on the other hand can promote the ion mobility of mending lithium material.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a positive electrode lithium supplementing material, a preparation method and application thereof.
Background
Lithium ion batteries have been attracting attention for use in mobile phones, electric vehicles, and other devices due to their long cycle life and high specific energy. However, during the first charge of a lithium ion battery with graphite as the negative electrode, 10% of active lithium from the positive electrode is consumed to form a solid electrolyte phase layer on the surface of the negative electrode, thereby reducing the specific energy of the existing lithium ion battery. In order to solve this problem, many studies have been conducted to compensate for the loss of active lithium in the first cycle of a lithium ion battery.
The lithium sulfide has 1166mAh/g high theoretical capacity, and is a promising anode lithium supplementing material. However, lithium-rich materials represented by lithium sulfide and the like are used as positive electrode lithium supplementing materials, the electronic and ionic conductivities are low, the internal lithium removal difficulty is caused by large particle size, and meanwhile, the application of the materials is further limited by the high sensitivity of the materials to water. In order to solve the above problems, it is necessary to promote the application of lithium-rich materials such as lithium sulfide as positive electrode lithium supplementing materials by improving the packaging technology.
Disclosure of Invention
In view of this, an object of the present application is to provide a positive electrode lithium-supplementing material, wherein a first shell layer containing reinforcing particles is coated on a lithium-rich material core, wherein the arrangement of the reinforcing particles can promote the stability of the first shell layer on one hand, prevent the lithium-supplementing material from being in direct contact with an electrolyte due to the easy damage of the coating layer, and can promote the ion mobility of the lithium-supplementing material by manufacturing a nanoscale lithium-rich core through a physical confinement.
Another object of the present application is to provide a method for preparing a positive electrode lithium supplementing material.
It is yet another object of the present application to provide a lithium-rich positive electrode.
It is still another object of the present application to provide a secondary battery.
To achieve the above object, an embodiment of a first aspect of the present application provides a positive electrode lithium supplementing material, including:
a lithium-rich core material;
the first shell layer is arranged on the outer surface of the lithium-rich core material, and reinforcing particles are embedded on the surface and/or the inside of the first shell layer.
In some embodiments of the present application, the reinforcing particles are distributed in a close-packed form on the first shell layer in which they reside.
In some embodiments of the present application, the reinforcing particles comprise one or more of silica nanoparticles and nano-metal oxides.
In some embodiments of the present application, the reinforcing particles have a particle size in the range of 5-50nm.
In some embodiments of the present application, the first shell layer is a hollow shell layer.
In some embodiments of the present application, the first shell has an inner diameter ranging from 50 to 500nm, the first shell has an outer diameter ranging from 70 to 570nm, and the difference between the inner diameter and the outer diameter of the first shell is no more than 100nm.
In some embodiments of the present application, the lithium-rich core material is a dissolvable renewable lithium-containing compound.
In some embodiments of the present application, the material of the first shell layer is a carbon material or a heteroatom doped carbon material.
In some embodiments of the present application, the soluble renewable lithium-containing compound comprises one or more of lithium sulfide, lithium phosphide, lithium bromide, lithium iodide.
In some embodiments of the present application, the positive electrode lithium supplementing material further includes a second shell layer, where the second shell layer covers the first shell layer and the outer surface of the reinforcing particle.
In some embodiments of the present application, the second shell layer includes at least one of an isolation encapsulation layer, an ion conductor encapsulation layer, and an electronic conductor encapsulation layer.
In some embodiments of the present application, the mass ratio of the lithium-rich core material, all shell materials, and the reinforcing particles is 80: (5-10): (10-15).
In some embodiments of the present application, the lithium-rich core material has a diameter of 50-500nm.
In some embodiments of the present application, the portion of the lithium-rich core material other than the outer surface constitutes a cladding layer, and the thickness of the cladding layer is 50-100nm.
In order to achieve the above object, a second aspect of the present application provides a method for preparing a positive electrode lithium-supplementing material, including:
preparing a first shell skeleton containing reinforcing particles by adopting a template sacrificial method;
and forming a lithium-rich material inside the first shell skeleton containing the reinforcing particles by adopting an impregnation method, and then sintering to obtain the positive electrode lithium supplementing material.
In some embodiments of the present application, the first shell scaffold containing reinforcing particles is prepared using a template sacrificial process comprising:
and coating the high molecular polymer microsphere serving as a template by a first shell layer source material, covalently grafting the reinforced particles, and soaking to remove the template.
To achieve the above objective, an embodiment of a third aspect of the present application provides a lithium-rich positive electrode, which includes a positive electrode active material, where the positive electrode active material includes a positive electrode lithium-supplementing material according to an embodiment of the present application or a positive electrode lithium-supplementing material prepared by a method for preparing a positive electrode lithium-supplementing material according to an embodiment of the present application.
To achieve the above object, a fourth aspect of the present application provides a secondary battery, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the lithium-rich positive electrode of the embodiments of the present application.
The positive electrode lithium supplementing material provided by the embodiment of the application has the beneficial effects that:
(1) The lithium-rich material has a core-shell structure, wherein a first shell layer containing reinforcing particles is coated on a lithium-rich material core, the arrangement of the reinforcing particles can promote the stability of the first shell layer on one hand, prevent the lithium-supplementing material from being in direct contact with electrolyte due to the fact that a coating layer is easy to damage, and can produce a nanoscale lithium-rich core through a physical limit domain on the other hand, so that the ion mobility of the lithium-supplementing material is promoted.
(2) The core-shell structure can also effectively limit the shape and the size of the lithium-rich core material particles, and simultaneously reduce the direct contact area of the lithium-rich core material of the positive electrode lithium-supplementing material and water, thereby reducing the occurrence of side reactions.
(3) The carbon material or the heteroatom doped carbon material is selected as the first shell layer, so that the conductivity of the positive electrode lithium supplementing material can be enhanced, and the battery performance of the positive electrode lithium supplementing material can be improved.
Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic structural diagram of a positive electrode lithium supplementing material according to an embodiment of the present application.
Reference numerals:
1-a lithium-rich core material; 2-a first shell layer; 3-reinforcing particles; 4-a second shell layer.
Detailed Description
Embodiments of the present application, examples of which are illustrated in the accompanying drawings, are described in detail below. The embodiments described below by referring to the drawings are exemplary and intended for the purpose of explaining the present application and are not to be construed as limiting the present application.
In the application, the disclosure of numerical ranges includes disclosure of all values and further sub-ranges within the entire range, including endpoints and sub-ranges given for these ranges.
In the application, the related raw materials, equipment and the like are all raw materials and equipment which can be self-made by commercial paths or known methods unless specified otherwise; the methods involved, unless otherwise specified, are all conventional.
A positive electrode lithium supplementing material according to an embodiment of the present application is described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural view of a positive electrode lithium supplementing material according to an embodiment of the present application.
As shown in fig. 1, the positive electrode lithium supplementing material in the embodiment of the application includes a lithium-rich core material 1 and a first shell layer 2, the first shell layer 2 is disposed on the outer surface of the lithium-rich core material 1, and reinforcing particles 3 are embedded on the surface and/or the inside of the first shell layer 2.
The positive electrode lithium supplementing material has a core-shell structure, wherein a first shell layer containing reinforcing particles is coated on a lithium-rich material core, the stability of the first shell layer can be improved due to the arrangement of the reinforcing particles, the lithium supplementing material is prevented from being in direct contact with electrolyte due to the fact that a coating layer is easy to damage, and the nanoscale lithium-rich core can be manufactured through physical limiting areas, so that the ion mobility of the lithium supplementing material is improved.
In some embodiments of the present application, the reinforcing particles are distributed in a close-packed form on the first shell layer in which they reside. The reinforcing particles are distributed on the first shell layer where the reinforcing particles are in a close-packed mode, because the reinforcing particles prepared in the subsequent preparation method of the positive electrode material are nano microspheres, and spontaneously agglomerate to form a close-packed structure due to the overlarge specific surface area. When the number of the first shell layers is plural, and reinforcing particles are distributed on the surfaces and/or the interiors of the plural first shell layers, the stacking densities of the reinforcing particles on the respective first shell layers may be the same or different; preferably, when different, the packing density of the reinforcing particles on the innermost first shell layer is maximized.
In some embodiments of the present application, the reinforcing particles include, but are not limited to, one or more of silica nanoparticles and nano-metal oxides. As non-limiting examples, nano-metal oxides include, but are not limited to, one or more of nano-titanium dioxide, nano-zinc oxide, nano-aluminum oxide, nano-zirconium oxide, nano-cerium oxide, nano-iron oxide. Selecting one or more of silica nanoparticles and nano-metal oxides as reinforcing particles can enhance ion conductivity and inhibit cation disorder within the crystal structure by providing active sites for ion diffusion, while providing a protective layer, inhibiting reaction between the positive electrode and the electrolyte.
In some embodiments of the present application, the particle size of the reinforcing particles includes, but is not limited to, between 5 and 50nm, for example, the upper limit may also include, but is not limited to, 60nm, 75nm, 100nm, 125nm, etc., and the lower limit may also include, but is not limited to, 0.5nm, 1nm, 2nm, 3nm, etc. The particle size of the reinforcing particles is within the above range, and the effect of the support structure can be achieved; if the specific surface area is smaller than the lower limit, the specific surface area is too large, the agglomeration is serious, and the internal resistance is increased; is larger than the upper limit, is separated from the first shell layer, and has no reinforcing effect.
It is understood that the reinforcing particles in the present application may be distributed only on the surface or inside the first shell layer, or may be distributed on the surface and inside the first shell layer at the same time. When the reinforcing particles are only distributed on the surface of the first shell layer, the wettability of the electrolyte is enhanced, and the structure enhancement effect is weak; when the reinforcing particles are only distributed in the first shell layer, the structure reinforcing effect is better; when the reinforcing particles are simultaneously distributed on the surface and the inside of the first shell layer (such as the reinforcing particles are embedded in the first shell layer, the reinforcing particles are partially positioned in the first shell layer and partially positioned outside the surface of the first shell layer), the electrolyte wettability is enhanced, and the structural stability is improved.
In some embodiments of the present application, the lithium-rich core material includes, but is not limited to, one or more of lithium-rich oxides, lithium nitride, lithium fluoride, lithium carbide, soluble renewable lithium-containing compounds. Among them, the soluble regenerated lithium-containing compounds include, but are not limited to, one or more of lithium sulfide, lithium phosphide, lithium bromide, lithium iodide. The term "soluble regeneration" in the lithium-containing compound which is soluble and regenerated in the present application is, in fact, recrystallization, and may be equivalent to soluble regeneration. Recrystallization is a process in which crystals are dissolved in a solvent or melted and then recrystallized from the solution or melt.
In some embodiments of the present application, the first shell layer is a hollow shell layer, and the structure can conveniently cover the lithium-rich core material, effectively limit the shape and the size of the core material, and promote the conductivity of the core material. Specifically, the inner diameter of the first shell layer ranges from 50 to 500nm, whereby the size of the lithium-rich core material can be limited to 50 to 500 nm. It will be appreciated that, particularly for soluble renewable lithium-containing compounds as lithium-rich core materials, such as lithium sulfide, commercially available lithium sulfide has a relatively large particle size, typically on the order of microns, and poor electrical conductivity. According to the method, the shell layer with the hollow structure can be prepared by adopting the template sacrificial method, and then lithium sulfide enters the hollow shell layer by adopting the impregnation method to form the lithium-rich core material, so that the particle size of the lithium sulfide can be limited below the nanometer level, and the conductivity of the lithium sulfide serving as the lithium-rich material is improved. The outer diameter of the first shell layer ranges from 70 to 570nm, and the difference between the inner diameter and the outer diameter of the first shell layer is not more than 100nm.
In some embodiments of the present application, in order to further improve stability of the positive electrode lithium-supplementing material, the number of the first shell layers may be set to be more than 2, and a plurality of first shell layers are sequentially set from a side close to the lithium-rich core material to a side far away from the lithium-rich core material (the latter is coated on the former surface), where reinforcing particles must be distributed on the surface and/or the inside of the first shell layer located at the innermost side (nearest to the lithium-rich core material), so that collapse of the hollow structure of the whole first shell layer can be prevented, the first shell layer material source is connected through covalent bonds or hydrogen bonds, and the reinforcing particles may or may not be distributed on the surface and/or the inside of the rest of the first shell layers, and when the reinforcing particles are also distributed on the surface and/or the inside of the rest of the first shell layers, stability of the lithium-supplementing material may be further enhanced. Taking the case of embedding the first shell layer in the reinforcing particle as an example: in some embodiments of the present application, when the number of first shell layers is more than 2, the reinforcing particles are embedded only in the first shell layer located at the innermost side (the conductive coating layer nearest to the lithium-rich core material), so that collapse of the hollow shell structure can be prevented, and the source of conductive coating layer material is connected by covalent or hydrogen bonding. In other embodiments of the present application, the reinforcing particles may be embedded within the first shell layer located innermost and between the first shell layer located innermost and the first shell layer located outermost (furthest from the lithium-rich core material). In further embodiments of the present application, the reinforcing particles may be embedded within the first shell layer located innermost and the first shell layer located outermost. In further embodiments of the present application, the reinforcing particles may be embedded within all of the first shell layers. As one possible example, the hollow shell layer of the positive electrode lithium-compensating material of the present application includes only one conductive coating layer within which the reinforcing particles are embedded. When reinforcing particles are embedded in a certain first shell layer, the first shell layer positioned outside and adjacent to the reinforcing particles is coated on the outer surfaces of the first shell layer and the reinforcing particles embedded in the first shell layer. In addition, the number of the first shell layers is preferably controlled within a reasonable range, for example, including but not limited to below 5, and exceeding 5 can increase the internal resistance of the material and reduce the energy density.
It should be noted that, in the present application, the reinforcing particles select one or more of silica nanoparticles and nano metal oxides, which are present only in the form of particles, but form doping in the portion in contact with the core during sintering, which has an advantageous effect.
In some embodiments of the present application, the material of the first shell layer is a carbon material, wherein the carbon material includes, but is not limited to, one or more of graphite, amorphous carbon, hard carbon, carbon fiber, and carbon nanotube. In other embodiments, the material of the first shell layer is a heteroatom-doped carbon material, wherein the heteroatom-doped carbon material includes, but is not limited to, one or more of nitrogen-doped carbon, sulfur-doped carbon, and phosphorus-doped carbon. The material of the first shell layer is carbon material or heteroatom doped carbon material, so that the conductivity of the positive electrode lithium supplementing material can be enhanced, and the battery performance of the positive electrode lithium supplementing material can be improved.
In some embodiments of the present application, in order to further improve the compactness and conductivity of the entire coating layer of the lithium-rich core material, the positive electrode lithium supplementing material of the present application further includes a second shell layer 4, where the second shell layer 4 is coated on the outer surfaces of the first shell layer 2 and the reinforcing particles 3. When the number of the first shell layers is plural, the second shell layer covers the outer surface of the first shell layer located at the outermost side (farthest from the lithium-rich core material), or covers the outer surface of the first shell layer and the reinforcing particle located at the outermost side (farthest from the lithium-rich core material). The second shell layer is a conductive encapsulation layer, including but not limited to at least one of an isolation encapsulation layer, an ion conductor encapsulation layer, and an electronic conductor encapsulation layer. Wherein, the material of the isolation packaging layer comprises one or more of ceramic, high molecular polymer and carbon material, preferably carbon material. The material of the electronic conductor encapsulation layer includes, but is not limited to, at least one of a carbon material, a conductive polymer, or a conductive oxide, preferably a carbon material. The material of the ion conductor encapsulation layer includes, but is not limited to, at least one of perovskite type, NASICON type, garnet type, or polymer type solid state electrolytes. As one possible example, the material of the second shell layer is a carbon material, and the carbon material of the second shell layer includes, but is not limited to, one or more of graphite, amorphous carbon, hard carbon, carbon nanotubes, and graphene sheets.
As a possible example, as shown in fig. 1, the positive electrode lithium supplementing material of the present application includes a lithium-rich core material 1, a first shell layer 2, reinforcing particles 3 and a second shell layer 4, where the number of the first shell layers 2 is 1, the first shell layers 2 are disposed on the outer surface of the lithium-rich core material 1, the reinforcing particles 3 are embedded in the first shell layers 2, the first shell layers 2 and the second shell layers 4 are carbon layers, and the second shell layers 4 are coated on the outer surfaces of the first shell layers 2 and the reinforcing particles 3.
In some embodiments of the present application, the mass ratio of the lithium-rich core material, all shell materials, all reinforcing particles, is 80: (5-10): (10-15). As non-limiting examples, the mass ratio of the lithium-rich core material, all shell materials, all reinforcing particles, three, includes, but is not limited to 80:5: 10. 80:7.5: 10. 80:10: 10. 80:5:12.5, 80:5: 15. 80:10:12.5 or 80:10:15, etc. The mass ratio of the lithium-rich core material to the shell material to the reinforcing particles is in the range, so that the nano lithium-rich core material can be effectively limited; the mass ratio is less than 80:5:10, the lithium-rich core material cannot be completely coated; the mass ratio is greater than 80:10:15, the coating is too thick, reducing the energy density. When the positive electrode lithium supplementing material only comprises a first shell layer, all shell layer materials are first shell layer materials; when the positive electrode lithium supplementing material comprises a first shell layer and a second shell layer, the positive electrode lithium supplementing material is the first shell layer material and the second shell layer material. The explanation of the reinforcing particles is similar and will not be repeated here.
In some embodiments of the present application, the lithium-rich core material has a diameter of 50-500nm. As non-limiting examples, lithium-rich core material diameters include, but are not limited to, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, or the like. The diameter of the lithium-rich core material is within the range, so that the capacity advantage can be exerted; less than 50nm, the energy density is affected; above 500nm, the capacity decreases.
In some embodiments of the present application, the portion of the positive electrode lithium-supplementing material other than the outer surface of the lithium-rich core material constitutes a coating layer, and the thickness of the coating layer is 50-100nm. As non-limiting examples, the thickness of the cladding layer includes, but is not limited to, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or the like. The thickness of the coating layer is in the range, so that the conductivity of the material can be improved; less than 50nm, the moisture is easy to contact and react with the kernel; greater than 100nm increases the lithium ion transfer resistance. In the case of the lithium-rich core material, the portion other than the outer surface of the lithium-rich core material is, for example, a portion between the side surface of the first shell layer 2 adjacent to the lithium-rich core material 1 and the outer surface of the second shell layer 4 in the structure shown in fig. 1.
In the present application, when the number of the first shell layers is plural and the number of the second shell layers is plural, the total thickness of the coating layers is still within the above range, but the thickness of each first shell layer may be the same or different, and the thickness of each second shell layer may be the same or different. In addition, the materials of the first shell layers can be the same or different, and the materials of the second shell layers can be the same or different.
The preparation method of the positive electrode lithium supplementing material comprises the following steps:
s101, preparing a first shell skeleton containing reinforcing particles by adopting a template sacrificial method.
The template sacrificial method of the present application is also referred to as a sacrificial method or a template sacrificial packaging method.
In some embodiments of the present application, a template sacrificial process is used to prepare a first shell scaffold containing reinforcing particles, comprising: and coating the high molecular polymer microsphere serving as a template by a first shell layer source material, covalently grafting the reinforced particles, and soaking to remove the template.
In some embodiments of the present application, the high molecular polymer microspheres include, but are not limited to, one or more of Polymethylmethacrylate (PMMA) microspheres, polystyrene (PS) microspheres. Wherein the particle size of the template includes, but is not limited to, 50-500nm.
In some embodiments of the present application, the first shell layer source material includes, but is not limited to, one or more of polyethylene oxide, polyaniline, polyacrylonitrile, polyvinyl alcohol, polyvinylpyrrolidone, polypyrrole, sucrose, glucose, phenolic resin, gelatin, melamine, protein, furfural, graphite oxide, graphene, polydopamine, bacterial cellulose.
In some embodiments of the present application, the mass ratio of template to first shell layer source material is 9-1:1-1. As non-limiting examples, the mass ratio of template to first shell layer source material includes, but is not limited to, 9:1, 7:1, 5:1, or 1:1, etc. The mass ratio of the template to the first shell layer source material is within the above range, and the template can be completely coated.
In some embodiments of the present application, the reaction conditions for covalently grafting the reinforcing particles are: the reaction temperature is 25-60 ℃, the reaction time is 3-10h, and the reaction is carried out under the stirring condition.
The reaction temperature of the covalent grafting-enhancing particles includes, but is not limited to, 25℃30℃35℃40℃45℃50℃55℃60℃and the like. The reaction time of the covalently grafted reinforcing particles includes, but is not limited to, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc.
In some embodiments of the present application, the template is removed by soaking with an organic solvent, including but not limited to at least one of acetone, ethyl acetate, dichloroethane, xylene.
The first shell skeleton containing the reinforcing particles prepared here is not the final form of the first shell in the positive electrode lithium-supplementing material. In addition, during covalent grafting, reinforcing particle source solutions are employed, including but not limited to ethyl orthosilicate ethanol solution, n-butyl titanate ethanol solution, aluminum isopropoxide ethanol solution, and the like.
S102, forming a lithium-rich material inside a first shell skeleton containing reinforcing particles by adopting an impregnation method, and then sintering to obtain the positive electrode lithium supplementing material.
In some embodiments of the present application, forming a lithium-rich material within a first shell layer comprising reinforcing particles using an impregnation process comprises: the first shell layer containing the reinforcing particles is placed in a glove box, immersed in a polar solvent solution of the lithium-rich core material, and heated to remove the polar solvent. Wherein the polar solvent includes, but is not limited to, one or more of ethanol, glycerol, propylene glycol, and the like. The heating temperature is set so that the polar solvent may be volatilized.
In some embodiments of the present application, the molar concentration of the lithium-rich core material includes, but is not limited to, 0.01-0.1 mol/L. As non-limiting examples, the molar concentration of the lithium-rich core material includes, but is not limited to, 0.01mol/L, 0.02mol/L, 0.03mol/L, 0.04mol/L, 0.05mol/L, 0.06mol/L, 0.07mol/L, 0.08mol/L, 0.09mol/L, or 0.1mol/L, etc.
In the present application, the purpose of sintering is to convert the first shell skeleton containing reinforcing particles obtained in step S101 into the first shell containing reinforcing particles in the positive electrode lithium-supplementing material.
In some embodiments of the present application, sintering is performed in an inert atmosphere including, but not limited to, one or more of nitrogen, argon, helium, and the like.
In some embodiments of the present application, the sintering temperature is 300-500 ℃. As non-limiting examples, sintering temperatures include, but are not limited to, 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, or the like.
In some embodiments of the present application, the sintering time is 1 to 3 hours. As non-limiting examples, sintering times include, but are not limited to, 1h, 1.5h, 2h, 2.5h, 3h, or the like.
In some embodiments of the present application, sintering may be performed in a tube furnace, rotary furnace, box furnace, roller kiln, pusher kiln, fluidized bed, or the like.
In some embodiments of the present application, when the number of first shell layers is 2 or more and each first shell layer contains reinforcing particles, then each first shell layer containing reinforcing particles is further added, step S101 is repeated once more before step S102, except that the first shell layer containing reinforcing particles located at the outermost side (farthest from the lithium-rich core material) is prepared, and the process of "soaking removal template" is removed.
In some embodiments of the present application, when the number of first shell layers is 2 or more, and the first shell layer located at the innermost side (closest to the lithium-rich core material) contains reinforcing particles, the remaining first shell layers partially contain reinforcing particles and partially do not contain reinforcing particles, then each of the first shell layers is one more, before proceeding to step S102:
when the first shell layer contains reinforcing particles, repeating step S101 once, but removing the "soaking removal template" process;
when the first shell layer does not contain reinforcing particles, repeating the step S101 once, but removing the covalent grafting reinforcing particles, and soaking to remove the template;
the template is removed by soaking until the last first shell layer is formed by the method described above, in either case.
In some embodiments of the present application, when the positive electrode lithium-compensating material contains the second shell layer, the preparation method of the positive electrode lithium-compensating material further includes a step of forming the second shell layer using a chemical vapor deposition method (CVD method) after step S102.
The method of forming the second shell layer in the present application is not limited to the chemical vapor deposition method (CVD method), and at least one of a sol-gel method, a solution method, a solid phase method, and the like may be used.
As a possible example, the preparation method of the positive electrode material of the embodiment of the present application includes the following steps:
(1) Preparing a first shell scaffold containing reinforcing particles: adding polymethyl methacrylate (PMMA) microspheres with the particle size of 50-500nm into 0.1-2mol/L dopamine hydrochloride aqueous solution, adding 100-500mg ammonium bicarbonate and 5ml 0.01mol/L ethyl orthosilicate ethanol solution, stirring at 25-60 ℃ for reaction for 3-10 hours, and then immersing and washing with acetone to remove the polymethyl methacrylate (PMMA) microspheres, thereby obtaining the nano silicon dioxide microsphere reinforced coating skeleton shell (namely the first shell skeleton containing reinforced particles).
(2) Preparing an intermediate product: and (3) putting the first shell skeleton containing the reinforced particles obtained in the step (1) into a glove box, immersing the first shell skeleton into 0.01-0.1mol/L lithium sulfide ethanol solution, and heating ethanol for volatilization to obtain an intermediate product.
(3) Preparing a first shell-coated lithium-rich core material containing reinforcing particles: transferring the intermediate product obtained in the step (2) into a tube furnace, and heating for 1-3h to sinter at 300-500 ℃ in an inert atmosphere to obtain the first shell-layer-coated lithium-rich core material containing reinforcing particles.
(4) Preparing a second shell layer: and (3) sintering the mixture for 40 minutes at 700 ℃ in a methane atmosphere by adopting a Chemical Vapor Deposition (CVD) method, and forming a graphite second shell layer on the outer surface of the lithium-rich core material coated by the first shell layer containing the reinforced particles obtained in the step (3), thereby obtaining the anode lithium supplementing material.
The lithium-rich positive electrode comprises a positive electrode active material, wherein the positive electrode active material comprises the positive electrode lithium supplementing material or the positive electrode lithium supplementing material prepared by the preparation method of the positive electrode lithium supplementing material.
In some embodiments of the present application, the positive electrode lithium supplementing material is present in an amount of 0.5 to 15wt% of the total positive electrode active material. As a non-limiting example, the positive electrode lithium supplementing material may be contained in an amount of 3wt%, 6wt%, 9wt%, 12wt%, or 15wt% of the entire positive electrode active material.
In some embodiments of the present application, the positive electrode active material may further include at least one of a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. The positive electrode active material includes, but is not limited to, one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadium fluorophosphate, lithium titanate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate. The positive electrode active material can perform intercalation and deintercalation, alloying and dealloying, or plating and exfoliation of lithium. Positive electrode conductive agents include, but are not limited to, one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes. The positive electrode conductive agent is added into the positive electrode material to enhance the conductivity of the electrode material layer, improve the conductivity of the lithium supplementing material and facilitate the transmission of electrons and ions. The positive electrode binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose, and polyacrylic acid.
In some embodiments of the present application, the lithium-rich positive electrode further comprises a current collector, which may optionally comprise aluminum or any other suitable conductive metal foil known to those skilled in the art (such as solid or mesh or cover foil), a metal grid or mesh, or a porous metal. In certain variations, the surface of the current collector may comprise a surface treated (e.g., carbon coated and/or etched) metal foil.
The secondary battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the positive electrode is the lithium-rich positive electrode.
In some embodiments of the present application, the positive electrode tab, separator and negative electrode tab may be processed to form a secondary battery using a lamination process or a winding process. It should be noted that the secondary battery according to the embodiment of the present application includes, but is not limited to, a lithium ion battery.
The negative electrode sheet, electrolyte, separator and the like of the secondary battery in the embodiment of the application are not particularly limited, and can be applied to any battery system.
The secondary battery of the embodiment of the application can be widely applied to the fields of new energy power automobiles, aerospace, electronic products and the like.
The preparation method of the positive electrode lithium supplementing material, the lithium-rich positive electrode and the secondary battery have the beneficial effects of the positive electrode lithium supplementing material.
Certain features of the present technology are further illustrated in the following non-limiting examples.
The raw materials used in the following non-limiting examples and comparative examples were commercially available materials without purification treatment, and were all of analytical pure reagent (AR) grade.
1. Examples and comparative examples
Example 1
As shown in fig. 1, the positive electrode lithium supplementing material of the present embodiment includes a lithium-rich core material 1, a first shell layer 2, reinforcing particles 3, and a second shell layer 4, wherein: the lithium-rich core material is lithium sulfide (Li) 2 S) coating a first shell layer 2 on the surface of a lithium-rich core material, wherein the first shell layer 2 is made of nitrogen-doped carbon nanotubes, reinforcing particles 3 are embedded in the first shell layer 2, the reinforcing particles 3 adopt silica nano particles with the particle size of 20nm, and the reinforcing particles 3 are distributed in the first shell layer 2 in a close-packed mode; the second shell layer 4 is coated on the outer surfaces of the first shell layer 2 and the reinforced particles 3, the second shell layer 4 is made of graphite, the number of the second shell layer 4 and the number of the first shell layers 2 are 1, the second shell layer 4 and the first shell layer 2 containing the reinforced particles 3 jointly form a coating layer, the mass ratio of the lithium-rich core material to all the shell layers (the first shell layer and the second shell layer) to the reinforced particles is 90:4:6, the diameter of the lithium-rich core material is 100nm, the thickness of the coating layer is 25nm, and the thickness of the first shell layer is 15nm.
The preparation method of the positive electrode lithium supplementing material of the embodiment comprises the following steps:
(1) Preparing a first shell scaffold containing reinforcing particles: 1g of polymethyl methacrylate (PMMA) microspheres with the particle size of 100nm are added into 20mL of 0.1mol/L dopamine hydrochloride aqueous solution, 250mg of ammonium bicarbonate and 5mL of 0.01mol/L ethyl orthosilicate ethanol solution are added, stirring is carried out at the temperature of 40 ℃ for 6.5h at the rotating speed of 400r/min, and then the polymethyl methacrylate (PMMA) microspheres are removed by soaking and washing with 20mL of acetone, so that the nano silicon dioxide microsphere reinforced coated skeleton shell (namely the first shell skeleton containing reinforced particles) is obtained.
(2) Preparing an intermediate product: and (3) placing the first shell skeleton containing the reinforced particles obtained in the step (1) into a vacuum glove box, immersing the first shell skeleton into 25ml of 2mol/L lithium sulfide ethanol solution for 30min, and heating to 60 ℃ to volatilize ethanol to obtain an intermediate product.
(3) Preparing a first shell-coated lithium-rich core material containing reinforcing particles: transferring the intermediate product obtained in the step (2) into a tube furnace, and heating at 400 ℃ for 2h to sinter in a nitrogen atmosphere to obtain the first shell-layer-coated lithium-rich core material containing reinforcing particles.
(4) Preparing a second shell layer: and (3) sintering the mixture for 40 minutes at 700 ℃ in a methane atmosphere by adopting a Chemical Vapor Deposition (CVD) method, and forming a graphite second shell layer on the outer surface of the lithium-rich core material coated by the first shell layer containing the reinforced particles obtained in the step (3), thereby obtaining the anode lithium supplementing material of the embodiment.
The lithium-rich positive electrode of the embodiment comprises a positive electrode current collector and a positive electrode active material coated on the surface of the positive electrode current collector, wherein the positive electrode current collector is aluminum foil, and the positive electrode active material comprises the following components in parts by weight: 93 parts of positive active material lithium iron phosphate, 2 parts of positive lithium supplementing material of the embodiment, 2 parts of positive conductive agent Super P, and 3 parts of positive binder polyvinylidene fluoride.
The secondary battery of the embodiment comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are overlapped between the positive electrode and the negative electrode, and the secondary battery comprises: the positive electrode is the lithium-rich positive electrode of the embodiment; the negative electrode comprises a negative electrode current collector and a negative electrode active material coated on the surface of the negative electrode current collector, wherein the negative electrode current collector is copper foil, and the negative electrode active material comprises the following components in parts by weight: 95 parts of negative electrode active material graphite, 2 parts of negative electrode conductive agent Super P, 0.5 part of thickener carboxymethyl cellulose (CMC) and 2.5 parts of negative electrode binder Styrene Butadiene Rubber (SBR); the diaphragm adopts a Polyethylene (PE) microporous diaphragm; the electrolyte comprises Ethylene Carbonate (EC), ethylmethyl carbonate (DEC) and LiPF 6 Wherein carbonic acidThe volume ratio of vinyl Ester (EC) to methyl ethyl carbonate (DEC) is 3:7, liPF 6 The concentration of (C) was 1mol/L.
The preparation method of the secondary battery of the embodiment comprises the following steps:
1) Preparing a positive electrode: n-methylpyrrolidone, lithium iron phosphate, positive electrode lithium supplementing material, positive electrode conductive agent Super P and positive electrode binder polyvinylidene fluoride are mixed according to the proportion of 100:93:2:2:3, mixing the materials according to the mass ratio, ball milling and stirring to obtain positive electrode slurry, wherein the ball milling time is 60min, the rotating speed is 30Hz, coating the positive electrode slurry on the surface of an aluminum foil, rolling, and vacuum drying overnight at 100 ℃ to obtain the positive electrode plate.
2) Preparing a negative electrode: the negative electrode active material (graphite), a negative electrode conductive agent (conductive carbon black, super P), a thickener (carboxymethyl cellulose, CMC) and a negative electrode binder (styrene butadiene rubber, SBR) are mixed according to the mass ratio of 95:2:0.5:2.5, placing the mixture in deionized water, uniformly mixing to prepare negative electrode slurry, coating the negative electrode slurry on the surface of a current collector copper foil, and obtaining a negative electrode plate after the procedures of drying, rolling and secondary drying.
3) Preparing an electrolyte: mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (DEC) in a volume ratio of 3:7, and adding LiPF 6 Electrolyte is formed, liPF 6 The concentration of (C) was 1mol/L.
4) Secondary battery (lithium ion battery) assembly: and assembling the lithium anode, the diaphragm, the electrolyte and the anode in a glove box in an inert nitrogen atmosphere according to the assembling sequence of the lithium anode, the diaphragm, the electrolyte and the anode to obtain the lithium ion battery.
Example 2
This embodiment is substantially the same as embodiment 1 except that:
the positive electrode lithium-supplementing material of this embodiment does not include the second shell layer 4.
The preparation method of the positive electrode lithium supplementing material of the embodiment does not include the step (4), and the lithium-rich core material coated by the first shell layer containing the reinforcing particles obtained in the step (3) is the positive electrode lithium supplementing material of the embodiment.
Example 3
This embodiment is substantially the same as embodiment 1 except that:
this embodimentIn the positive electrode lithium supplementing material, the lithium-rich core material is lithium phosphide (Li 3 P)。
Example 4
This embodiment is substantially the same as embodiment 1 except that:
the number of the first shell layers of the positive electrode lithium supplementing material in this embodiment is 2, and for convenience of description, the first shell layers a and B are defined; the first shell layer A and the first shell layer B are sequentially arranged from one side close to the lithium-rich core material to one side far away from the lithium-rich core material, silica nanoparticle reinforced particles with the particle size of 20nm are embedded in the first shell layer A and the first shell layer B, and the reinforced particles are distributed in the first shell layer in a close-packed mode; the second shell layer is coated on the outer surfaces of the first shell layer B and the reinforcing particles thereof, the second shell layer and the two first shell layers containing the reinforcing particles jointly form a coating layer, the mass ratio of the lithium-rich core material to all the shell layers (the first shell layer A and the first shell layer B) to all the reinforcing particles is 90:4:6, the diameter of the lithium-rich core material is 100nm, and the thickness of the coating layer is 30nm.
The preparation method of the positive electrode lithium supplementing material of the embodiment comprises the following steps:
(1) Preparing a first shell layer a containing reinforcing particles: 1g of polymethyl methacrylate (PMMA) microspheres with the particle size of 100nm are added into 20mL of 0.1mol/L dopamine hydrochloride aqueous solution, 250mg of ammonium bicarbonate and 2.5mL of 0.01mol/L ethyl orthosilicate ethanol solution are added, and stirring reaction is carried out for 6.5h at the temperature of 40 ℃ at the rotating speed of 400r/min, so that a first shell layer A containing reinforcing particles is obtained.
(2) Preparing a first shell layer B containing reinforcing particles: the first shell layer A containing the reinforced particles after filtration and drying is added into 20mL of 0.1mol/L dopamine hydrochloride aqueous solution, 250mg of ammonium bicarbonate and 2.5mL of 0.01mol/L ethyl orthosilicate ethanol solution are added, stirring is carried out at 40 ℃ for 6.5h at the rotating speed of 400r/min, and then the polymethyl methacrylate (PMMA) microspheres are removed by soaking and washing with 20mL of acetone, so that the first shell layers B and A containing the reinforced particles are obtained.
(3) Preparing an intermediate product: and (3) placing the first shell skeleton containing the reinforced particles obtained in the step (2) into a vacuum glove box, immersing the first shell skeleton into 25L of 2mol/L lithium sulfide ethanol solution for 30min, and heating to 60 ℃ to volatilize ethanol to obtain an intermediate product.
(4) Preparing a first shell-coated lithium-rich core material containing reinforcing particles: transferring the intermediate product obtained in the step (3) into a tube furnace, and heating at 400 ℃ for 2h to sinter in a nitrogen atmosphere to obtain the first shell-layer-coated lithium-rich core material containing reinforcing particles.
(5) Preparing a second shell layer: and (3) sintering the mixture for 40 minutes at 700 ℃ in a methane atmosphere by adopting a Chemical Vapor Deposition (CVD) method, and forming a graphite second shell layer on the outer surface of the lithium-rich core material coated by the first shell layer containing the reinforced particles obtained in the step (4), thereby obtaining the anode lithium supplementing material of the embodiment.
Example 5
This embodiment is substantially the same as embodiment 4 except that:
in the positive electrode lithium supplementing material, reinforcing particles are not embedded in the first shell layer B, and the mass ratio of the lithium-rich core material to all the shell layers (the first shell layer A and the first shell layer B) to all the reinforcing particles is 90:5:5.
In the preparation method of the positive electrode lithium supplementing material, the step (2) is deleted and 5ml of 0.01mol/L ethyl orthosilicate ethanol solution is stirred and reacted for 6.5h at the temperature of 40 ℃ at the rotating speed of 400 r/min.
Example 6
This embodiment is substantially the same as embodiment 4 except that:
in the positive electrode lithium supplementing material, the mass of the reinforcing particles embedded in the first shell layer A and the first shell layer B is halved, the stacking density is half of that of the embodiment 4, and the mass ratio of the lithium-rich core material to all the shell layers (the first shell layer A and the first shell layer B) to all the reinforcing particles is 90:7:3.
In the preparation method of the positive electrode lithium supplementing material, the dosage of the ethyl orthosilicate ethanol solution in the step (1) and the step (2) is halved.
Comparative example 1
This comparative example is substantially the same as example 1 except that:
the positive electrode lithium supplementing material of this comparative example is different from example 1 in that: the first shell layer is not provided with reinforcing particles. 2. Performance testing
1. Test method
(1) Moisture resistance test of positive electrode lithium supplementing material
The lithium ion batteries of each example and comparative example were tested for specific capacities at room temperature under different humidity conditions (25%, 20%, 10%) for different durations.
(2) Electrochemical Properties
Electrochemical performance tests such as 0.1C first discharge specific capacity, 1C first discharge specific capacity and the like are carried out on the lithium ion batteries of the examples and the comparative examples, and the test conditions are as follows: and (3) placing the lithium ion battery at room temperature for 24 hours, and then performing charge and discharge test, wherein the charge and discharge voltage is 2.5-4.2V.
2. Test results
The performance of the lithium ion batteries of examples 1 to 6 and comparative example 1 was tested, the wet resistance performance test results are shown in tables 1, 2 and 3, and the electrochemical performance test results are shown in table 4.
TABLE 1 specific capacities of lithium ion batteries at 15% humidity and 25℃for different times
TABLE 2 specific capacities of lithium ion batteries at 20% humidity and 25℃for different times
TABLE 3 specific capacities of lithium ion batteries at 25% humidity and 25℃shelf for different times
Table 4 results of electrochemical performance tests of lithium ion batteries of examples 1 to 6 and comparative example 1
As can be seen from tables 1 to 4, the multi-layered carbon coating reduces the contact of the core with moisture due to the stable metal nanoparticle reinforced structure, and the positive electrode lithium supplementing material exhibits excellent specific charge capacity in the carbonate-based electrolyte. Example 2 lacks protection of the outer carbon layer, is preserved in air at a certain humidity, the inner core contacts moisture and reacts immediately to form hydrogen sulfide, causing capacity fade; the inner core of the embodiment 3 is lithium phosphide, has a theoretical capacity of 1550mAh/g, and finally reaches a high specific charge capacity of 880mAh/g in the carbonate-based electrolyte at 0.1C; in the embodiment 4, the embodiment 5 and the embodiment 6, the number of layers of the first shell layers and the number of reinforcing particles are changed, and the plurality of first shell layers can improve the stability of the inner core in a certain humidity environment, but can also block the migration of lithium ions to a certain degree; comparative example 1 has no reinforcing particles, the shell structure is unstable and collapses when the template is immersed in acetone, and the subsequent recrystallization of lithium sulfide mostly grows on the surface of the shell and is extremely easy to directly react with air moisture, so that the final discharge specific capacity is low.
The terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., in this application, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (13)
1. A positive electrode lithium supplementing material, characterized by comprising:
A lithium-rich core material;
the first shell layer is arranged on the outer surface of the lithium-rich core material, and reinforcing particles are embedded on the surface and/or the inside of the first shell layer.
2. The positive electrode lithium-compensating material of claim 1, wherein the reinforcing particles are distributed in a close-packed form on the first shell layer in which they are located.
3. The positive electrode lithium-compensating material of claim 1, wherein the reinforcing particles comprise one or more of silica nanoparticles and nano-metal oxides;
and/or the particle size of the reinforcing particles is in the range of 5-50nm.
4. The positive electrode lithium-supplementing material according to claim 1, wherein the first shell layer is a hollow shell layer;
and/or the first shell has an inner diameter ranging from 50 to 500nm, an outer diameter ranging from 70 to 570nm, and a difference between the inner diameter and the outer diameter of the first shell is not more than 100nm.
And/or the lithium-rich core material is a soluble renewable lithium-containing compound.
5. The positive electrode lithium-supplementing material according to claim 4, wherein the material of the first shell layer is a carbon material or a heteroatom-doped carbon material;
and/or the soluble regenerated lithium-containing compound comprises one or more of lithium sulfide, lithium phosphide, lithium bromide, lithium iodide.
6. The positive electrode lithium-compensating material of claim 1, further comprising a second shell coating the first shell and the outer surface of the reinforcing particles.
7. The positive electrode lithium-compensating material of claim 6, wherein the second shell layer comprises at least one of an isolation encapsulation layer, an ion conductor encapsulation layer, and an electron conductor encapsulation layer.
8. The positive electrode lithium-supplementing material according to any one of claims 1 to 7, wherein a mass ratio of the lithium-rich core material, all shell materials, the reinforcing particles is 80: (5-10): (10-15).
9. The positive electrode lithium-supplementing material according to any one of claims 1 to 7, wherein the lithium-rich core material has a diameter of 50 to 500nm;
and/or the part except the outer surface of the lithium-rich core material forms a coating layer, and the thickness of the coating layer is 50-100nm.
10. The preparation method of the positive electrode lithium supplementing material is characterized by comprising the following steps of:
preparing a first shell skeleton containing reinforcing particles by adopting a template sacrificial method;
and forming a lithium-rich material inside the first shell skeleton containing the reinforcing particles by adopting an impregnation method, and then sintering to obtain the positive electrode lithium supplementing material.
11. The method for preparing a positive electrode lithium-compensating material of claim 10, wherein the preparing the first shell skeleton containing reinforcing particles by a template sacrificial method comprises:
and coating the high molecular polymer microsphere serving as a template by a first shell layer source material, covalently grafting the reinforced particles, and soaking to remove the template.
12. A lithium-rich positive electrode comprising a positive electrode active material comprising the positive electrode lithium-supplementing material according to any one of claims 1 to 10, or the positive electrode lithium-supplementing material produced by the production method according to claim 10 or 11.
13. A secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the lithium-rich positive electrode according to claim 12.
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