CN115295771A - Positive electrode composite material, preparation method thereof, positive electrode plate and secondary battery - Google Patents
Positive electrode composite material, preparation method thereof, positive electrode plate and secondary battery Download PDFInfo
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- CN115295771A CN115295771A CN202111289013.1A CN202111289013A CN115295771A CN 115295771 A CN115295771 A CN 115295771A CN 202111289013 A CN202111289013 A CN 202111289013A CN 115295771 A CN115295771 A CN 115295771A
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- lithium
- positive electrode
- composite material
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- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 208
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 193
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- 239000000654 additive Substances 0.000 claims abstract description 123
- 230000000996 additive effect Effects 0.000 claims abstract description 122
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000007774 positive electrode material Substances 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 41
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- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 claims description 11
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- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 claims description 4
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- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims description 3
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 3
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims description 3
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- 238000004519 manufacturing process Methods 0.000 claims 1
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Images
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
- H01M4/36—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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application belongs to the technical field of batteries, and particularly relates to a positive electrode composite material and a preparation method thereof, a positive plate and a secondary battery. The preparation method of the positive electrode composite material comprises the following steps: dissolving a lithium source, a nickel source and a positive active material in an anhydrous solvent, mixing and drying to obtain a composite precursor; and calcining the composite precursor to obtain the cathode composite material with a core-shell structure, wherein the core of the cathode composite material is a cathode active material, and the shell layer of the cathode composite material is a lithium supplement additive. According to the preparation method of the cathode composite material, the lithium supplement additive is uniformly and stably coated on the surface of the cathode active material while the lithium supplement additive is prepared, so that the process is simplified, and the lithium supplement additive and the cathode active material are stably combined and uniformly distributed. The method not only can compensate active lithium ions consumed by the formation of the SEI film during the first charge and discharge of the battery, improve the initial capacity, but also can improve the cycling stability of the battery.
Description
Technical Field
The application belongs to the technical field of batteries, and particularly relates to a positive electrode composite material and a preparation method thereof, a positive electrode plate and a secondary battery.
Background
With the rapid development of energy storage technology, the use of portable digital devices and vehicle-mounted power supplies is increasing, people have higher and higher requirements on the energy density of batteries, and the development of secondary batteries with large capacity, long service life and high safety is imperative. During the first charge and discharge process of the lithium ion battery, an SEI film is formed on the interface of a negative electrode material, and researches show that the SEI film mainly comprises LiF and Li 2 CO 3 、R-COOLi、R-CH 2 OLi and the like. The formation of SEI film is an irreversible process, li used to form SEI + Can not be inserted into the anode material during discharge, and consumes a part of Li in the anode material + Which in turn leads to irreversible capacity loss of the electrode material, reducing the capacity of the battery.
Currently, this capacity loss can be compensated by pre-replenishing lithium. The lithium pre-supplement technology is mainly divided into two types, one is a lithium supplement technology for a negative electrode material, the technology has higher requirements on the operating environment, and lithium supplement agents are generally metal lithium foil and inert lithium powder; and the other is a lithium supplementing technology for the anode material, and the technical requirement is relatively low. At present, the lithium supplement technology of the anode material is that the anode lithium supplement additive is prepared firstly, and then the prepared anode lithium supplement additive is mixed with the anode material, so that the preparation and mixing cost is increased; and the binding degree of the positive electrode lithium supplement material additive and the positive electrode material is poor, and the lithium supplement additive is easy to have the phenomena of uneven dispersion and the like in the positive electrode material, so that the stability of cyclic charge and discharge of the electrode is influenced.
Disclosure of Invention
The application aims to provide a positive electrode composite material and a preparation method thereof, a positive plate and a secondary battery, and aims to solve the problem that the existing positive electrode lithium supplement additive is poor in binding degree with a positive electrode material to a certain extent.
In order to achieve the purpose of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a method for preparing a positive electrode composite material, comprising the steps of:
dissolving a lithium source, a nickel source and a positive active material in an anhydrous solvent, mixing and drying to coat the surface of the positive active material with the lithium source and the nickel source to obtain a composite precursor;
and calcining the composite precursor to obtain the cathode composite material with a core-shell structure, wherein the core of the cathode composite material is a cathode active material, and the shell layer of the cathode composite material is a lithium supplement additive.
Further, the lithium source is selected from: niCo 3 、Ni(OH) 2 And NiO.
Further, the nickel source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of (1).
Further, the positive electrode material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganese iron phosphate, lithium manganate, lithium nickel cobalt aluminate and lithium nickel manganate.
Further, the anhydrous solvent is selected from: at least one of absolute ethyl alcohol, methanol and acetone.
Further, the conditions of the hybrid drying process include: stirring for 2-6 hours at the temperature of 80-100 ℃.
Further, the step of calcining treatment comprises: keeping the temperature of the composite precursor at 400-500 ℃ for 2-6 hours, heating to 680-780 ℃ and keeping the temperature for 12-24 hours.
Further, the lithium supplement additive is Li 2 NiO 2 The positive electrode material comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate.
Further, after the positive electrode composite material with the core-shell structure is obtained, the method further comprises the step of forming at least one of an isolation packaging layer, an ion conductor packaging layer and an electronic conductor packaging layer on the outer surface of the shell layer.
Further, in the positive electrode composite material, the mass percentage of the shell layer of the lithium supplement additive is 1-10%.
In a second aspect, the positive electrode composite material is of a core-shell structure and comprises a positive electrode active material inner core and a lithium supplement additive shell layer, wherein the lithium supplement additive shell layer is coated on the outer surface of the inner core in situ and is made of a lithium source and a nickel source.
Further, the nickel source is selected from: niCo 3 、Ni(OH) 2 And NiO.
Further, the lithium source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of (1).
Further, the lithium supplement additive shell layer comprises Li 2 NiO 2 The positive active material core comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate.
Furthermore, the outer surface of the lithium supplement additive shell layer also comprises at least one of an isolation packaging layer, an ion conductor packaging layer and an electron conductor packaging layer.
Furthermore, the thickness of the shell layer of the lithium supplement additive is 5-50 nm.
Further, in the positive electrode composite material, the mass percentage of the lithium supplement additive shell layer is 1-10%.
In a third aspect, the present application provides a positive electrode sheet, where the positive electrode sheet includes the positive electrode lithium supplement additive prepared by the above method, or includes the positive electrode lithium supplement additive.
In a fourth aspect, the present application provides a secondary battery comprising the positive electrode sheet described above.
According to the preparation method of the cathode composite material provided by the first aspect of the application, the lithium source, the nickel source and the cathode active material are dissolved in the anhydrous solvent, and are mixed and dried to be separated out and coated on the surface of the cathode active material, so that the composite precursor with the core-shell structure is formed. The adopted anhydrous solvent can effectively avoid the problems of nonuniform mixing of the precursor coating layer and the like caused by layering of the lithium source in the precipitation process. And then calcining the composite precursor, reacting and converting the lithium supplement additive precursor into a lithium supplement additive in the high-temperature calcining process, and generating a lithium supplement additive coating shell layer on the surface of the positive active material in situ to obtain the positive composite material. According to the preparation method of the cathode composite material, the lithium supplement additive is uniformly and stably coated on the surface of the cathode active material while the lithium supplement additive is prepared, so that the process is simplified, and the lithium supplement additive and the cathode active material are stably combined and uniformly distributed. The method not only can compensate active lithium ions consumed by the formation of the SEI film during the first charge and discharge of the battery, improve the initial capacity, but also can improve the cycling stability of the battery.
The cathode composite material provided by the second aspect of the application is of a core-shell structure and comprises a cathode active material inner core and a lithium supplement additive shell layer which is coated on the outer surface of the inner core in situ; on one hand, the shell layer is coated on the outer surface of the core in situ and is tightly combined with the anode active material, the lithium supplement additive is uniformly dispersed, and the lithium supplement effect is stable; on the other hand, the lithium supplement additive in the shell layer can effectively make up active lithium ions consumed by the formation of an SEI film during the first charge and discharge of the battery, so that the initial capacity is improved, and the energy density of the battery is further improved.
The positive plate provided by the third aspect of the present application comprises the positive electrode composite material, and the positive electrode composite material is of a core-shell structure and comprises a positive electrode active material core and a lithium supplement additive shell layer coated on the outer surface of the core in situ. The lithium supplement additive has good lithium supplement capacity, the shell layer of the lithium supplement additive is tightly combined with the positive active material, the lithium supplement additive is uniformly dispersed, the lithium supplement effect is stable, active lithium ions consumed by the formation of an SEI (solid electrolyte interphase) film during the first charge and discharge of the battery can be effectively compensated, and the energy density of the battery is improved.
According to the secondary battery provided by the fourth aspect of the application, the positive plate comprises the positive electrode composite material which takes the positive electrode active material as the core and is coated on the lithium supplement additive shell layer on the outer surface of the core in situ, so that active lithium ions consumed due to the formation of an SEI (solid electrolyte interphase) film when the battery is charged for the first time can be effectively compensated, the gram capacity of the positive plate is effectively maintained, and the capacity retention rate of the positive plate is improved. Therefore, the secondary battery provided by the application has high energy density and good capacity retention rate.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for preparing a positive electrode composite material provided in an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clearly apparent, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In this application, the term "and/or" describes an association relationship of associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (one) of a, b, or c," or "at least one (one) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.
It should be understood that, in various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weight of the related components mentioned in the description of the embodiments of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present application as long as it is scaled up or down according to the description of the embodiments of the present application. Specifically, the mass in the description of the embodiments of the present application may be in units of mass known in the chemical industry, such as μ g, mg, g, and kg.
The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another, and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
As shown in fig. 1, a first aspect of embodiments of the present application provides a method for preparing a positive electrode composite material, including the following steps:
s10, dissolving a lithium source, a nickel source and the positive active material in an anhydrous solvent, mixing and drying to coat the surface of the positive active material with the lithium source and the nickel source to obtain a composite precursor;
and S20, calcining the composite precursor to obtain the anode composite material with the core-shell structure, wherein the core of the anode composite material is an anode active material, and the shell of the anode composite material is a lithium supplement additive.
In the preparation method of the cathode composite material provided in the first aspect of the embodiment of the present application, a lithium source, a nickel source, and a cathode active material are dissolved in an anhydrous solvent, and after mixing and drying, the lithium source and the nickel source are precipitated and coated on the surface of the cathode active material, so as to form a composite precursor with a core-shell structure. The adopted anhydrous solvent can effectively avoid the problems of nonuniform mixing of the precursor coating layer and the like caused by layering of the lithium source in the precipitation process. And then calcining the composite precursor, reacting and converting the lithium supplement additive precursor into a lithium supplement additive in the high-temperature calcining process, and generating a lithium supplement additive coating shell layer on the surface of the positive active material in situ to obtain the positive composite material. According to the preparation method of the cathode composite material, the lithium supplement additive is uniformly and stably coated on the surface of the cathode active material while the lithium supplement additive is prepared, so that the process is simplified, and the lithium supplement additive and the cathode active material are stably combined and uniformly distributed. The method not only can compensate active lithium ions consumed by the formation of the SEI film during the first charge and discharge of the battery, improve the initial capacity, but also can improve the cycling stability of the battery.
In some embodiments, in step S10 above, the nickel source is selected from: niCo 3 、Ni(OH) 2 And NiO. In some embodiments, the lithium source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of (1). The lithium and nickel sources of the above examples of the present application were passed through the followingCalcination treatment to form Li 2 NiO 2 Lithium supplement additives having a relatively low charge plateau, in particular at 3.5V (vs Li/Li) + ) When decomposed with the transition from crystalline to amorphous phase; and the decomposed amorphous phase provides a delithiation capacity of not less than 360mAh/g at the first charge, so that Li 2 NiO 2 The lithium supplement additive has good lithium supplement effect and can provide charge/Li for charge compensation on the negative electrode + 。
In some embodiments, the positive electrode material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganese iron phosphate, lithium manganate, lithium nickel cobalt aluminate, lithium nickel cobalt manganate, lithium nickel manganese manganate; these positive electrode materials have high gram capacity, and are favorable for improving the energy density of the battery. However, in the first charge and discharge process of these cathode materials, since an SEI film is formed on the surface of the negative electrode, lithium ions are consumed, and the first effect and energy density of the entire battery are reduced. Li formed in situ with surface of positive electrode active material in embodiments of the present application 2 NiO 2 The lithium supplement additive is matched, so that consumed lithium ions can be effectively supplemented, and the first effect and the energy density of the whole battery are improved.
In some preferred embodiments, the positive electrode material comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate, and the lithium supplement additive is Li 2 NiO 2 And forming the nickel-rich ternary cathode material. The lithium supplement additive not only can supplement a lithium source for forming an SEI film, but also can play a role in synergy with a nickel source in the ternary cathode material in the lithium supplement additive, so that the reversible discharge specific capacity of the cathode composite material is improved.
In some embodiments, the lithium supplement additive is present in the positive electrode composite material in an amount of 1 to 10% by mass of the shell layer. If the mass ratio of the shell layer of the lithium supplement additive in the positive electrode composite material is too high, on one hand, the positive electrode composite material is easy to absorb water to cause gel failure of the positive electrode composite material when a positive plate is prepared by homogenizing; on the other hand, because the lithium supplement additive of the shell layer has basically irreversible lithium ions in the subsequent charge-discharge cycle process, the amount of lithium intercalation is very small, the capacity additionally provided in the cycle process is very small, and the amount of lithium ions consumed for forming an SEI film in charge-discharge is certain, if the content of the shell layer of the lithium supplement additive is too high, the proportion of the positive active material is reduced, so that the gram capacity of the positive composite material is reduced, and the energy density of the battery is reduced. If the mass ratio of the shell of the lithium supplement additive in the positive electrode composite material is too low, lithium ions consumed by an SEI film cannot be compensated and formed, so that the first effect and the energy density of the battery cannot be improved. In some embodiments, the mass percentage of the shell layer of the lithium supplement additive in the positive electrode composite material includes, but is not limited to, 1-2%, 2-5%, 5-7%, 7-9%, 9-10%, and the like.
In some embodiments, a lithium source, a nickel source and a positive electrode active material are dissolved in an anhydrous solvent, the lithium source and the nickel source are uniformly precipitated and coated on the surface of the positive electrode active material to form a precursor coating layer through a mixing and drying treatment, and the coated lithium supplement additive precursor is converted into a lithium supplement additive through a subsequent calcination treatment.
In some embodiments, the anhydrous solvent is selected from: on one hand, the anhydrous solvents have better dissolution and dispersion effects on a lithium source, a nickel source, a positive active material and the like, and on the other hand, the lithium source is easy to dissolve in water, if the solvents contain water, the lithium source is easy to be layered up and down in the mixing and drying process, so that the lithium source and the nickel source coated on the surface of the positive active material in the composite precursor are unevenly distributed, and the in-situ formation of a coating shell layer by a subsequent positive lithium supplement additive is influenced.
In some embodiments, a lithium source, a nickel source and a positive electrode active material are dissolved in an anhydrous solvent, and stirred for 2-6 hours at a temperature of 80-100 ℃ to slowly evaporate the solvent, i.e., the mixture is dried, and the lithium source and the nickel source of the lithium supplement additive are separated out and coated on the surface of the positive electrode active material to obtain a composite precursor. In some embodiments, the temperature condition of the mixing and drying may be 80-90 ℃, 90-100 ℃ or the like, and the time may be 2-3 hours, 3-4 hours, 4-5 hours, 5-6 hours or the like, until the solvent is sufficiently volatilized to form a coating shell layer of the precursor material.
In some embodiments, the steps described aboveIn step S20, the step of performing the calcination process on the composite precursor includes: keeping the temperature of the composite precursor at 400-500 ℃ for 2-6 hours, heating to 680-780 ℃ and keeping the temperature for 12-24 hours. In the embodiment of the application, the calcination treatment of the composite precursor adopts two stages, firstly, raw material components added by lithium supplement such as a lithium source are molten under the condition that the temperature is 400-500 ℃, and the composite precursor is kept warm for 2-6 hours at this stage, so that the lithium source, the nickel source and the cathode material are mixed in an ionic state, and all the components in the precursor are further mixed uniformly. Then heating to 680-780 ℃ and preserving the temperature for 12-24 hours to ensure that the lithium source and the nickel source fully react to generate Li 2 NiO 2 And (3) a compound of a lithium supplement additive. In some embodiments, the temperature ramp rate includes, but is not limited to, 1 to 10 deg.C/min, which is beneficial for improving the equilibrium of the reaction.
In some embodiments, after obtaining the positive electrode composite material with the core-shell structure, the method further includes a step of forming at least one of an isolation encapsulation layer, an ion conductor encapsulation layer, and an electron conductor encapsulation layer on the outer surface of the shell layer. The isolation packaging layer can effectively isolate moisture, oxygen and the like from contacting with the lithium supplement additive in the positive electrode composite material to destroy the material property, the stability of the positive electrode composite material is improved, the stable lithium supplement effect is realized, and the electrochemical performance of the positive electrode material is stabilized. The ion conductor packaging layer and the electron conductor packaging layer can improve the electron and ion conduction performance of the positive electrode composite material and improve the lithium extraction in the charging process.
In some embodiments, after the core-shell structured positive electrode composite material is obtained, one of the isolation encapsulation layer, the ion conductor encapsulation layer and the electronic conductor encapsulation layer can be formed separately, or more than two encapsulation layers can be prepared. For example, the lithium supplement additive shell layer can be a composite laminated structure of an isolation encapsulating layer and an electronic conductor encapsulating layer, and the isolation encapsulating layer is preferably coated on the outer surface of the lithium supplement additive shell layer, and the electronic conductor encapsulating layer is coated on the outer surface of the isolation encapsulating layer. Or a composite laminated structure of an isolation packaging layer and an ion conductor packaging layer, wherein the isolation packaging layer is coated on the outer surface of the lithium supplement additive shell layer, and the ion conductor packaging layer is coated on the outer surface of the isolation packaging layer. The lithium ion battery can also be a composite laminated structure of an isolation packaging layer, an electronic conductor packaging layer and an ion conductor packaging layer, and the preferred structure is that the isolation packaging layer is coated on the outer surface of the lithium supplement additive shell layer, the ion conductor packaging layer is coated on the outer surface of the isolation packaging layer, and the electronic conductor packaging layer is coated on the outer surface of the ion conductor packaging layer; or the isolation packaging layer is coated on the outer surface of the lithium supplement additive shell layer, the electronic conductor packaging layer is coated on the outer surface of the isolation packaging layer, and the ion conductor packaging layer is coated on the outer surface of the electronic conductor packaging layer.
In some embodiments, the barrier encapsulation layer protects the positive electrode composite, and particularly the shell of the lithium supplement additive, from contact with water and carbon dioxide in the environment. The material for preparing the isolation packaging layer comprises at least one of ceramic, high molecular polymer or carbon material, and further the thickness of the isolation packaging layer is 5-200nm.
In some embodiments, when the material of the isolation encapsulation layer is a ceramic layer, the ceramic target can be, but is not limited to, sputter-depositing the ceramic isolation encapsulation layer on the surface of the positive electrode composite material by magnetron sputtering, wherein the magnetron sputtering conditions are adjusted according to specific target properties.
In another embodiment, when the material of the isolation encapsulation layer is a high molecular polymer layer, the step of forming the high molecular polymer isolation encapsulation layer may be: and dispersing the positive electrode composite material in a solution containing a high molecular polymer, and then performing vacuum drying to form a compact polymer isolation packaging layer on the surface of the positive electrode composite material. Wherein the solvent of the solution is a solvent capable of uniformly dispersing or dissolving the high molecular polymer, such as one or more of N-methylpyrrolidone, methanol, ethanol, isopropanol, acetone, tetrahydrofuran and diethyl ether.
In another embodiment, when the material of the isolation encapsulation layer is a carbon material layer, the method for forming the carbon material isolation encapsulation layer comprises the following steps: and dispersing the positive electrode composite material in a solution containing a carbon source, drying, and then carbonizing to form a compact carbon isolation packaging layer on the surface of the positive electrode composite material. The carbon source may be, but is not limited to, PEO, and may be other carbon sources. The present invention is applicable to any positive electrode composite material as long as it can form a carbon source layer on the surface of the positive electrode composite material. Specifically, the positive electrode composite material and PEO are mixed uniformly, the PEO is heated to be melted and uniformly coated on the surface of the lithium source particles, the coated material is sintered in an inert atmosphere at 600 ℃, the temperature is kept for 16 hours, and a compact carbon layer is formed after the sintering is finished.
In some embodiments, the electron conductor encapsulation layer can enhance the electron conductivity of the encapsulation layer, thereby enhancing the electron conductivity of the lithium supplement additive, which facilitates reducing the impedance inside the electrode. The material for preparing the electronic conductor packaging layer comprises at least one of carbon material, conductive polymer or conductive oxide; the carbon material, the conductive polymer and the conductive oxide are all the materials of the electronic conductor packaging layer contained in the lithium supplement additive; the thickness of the electronic conductor packaging layer is 5-200nm. The method and conditions for forming the electron conductor encapsulation layer of the carbon material, the conductive polymer and the conductive oxide are specifically formed in accordance with the method for forming the carbon material, the conductive polymer or the conductive oxide. In some embodiments, the method of forming the electronic conductor encapsulation layer may use chemical deposition, magnetron sputtering, or atomic layer deposition to form the isolated conductive encapsulation layer. In some embodiments, the coating with Li is performed by magnetron sputtering or atomic layer deposition 2 NiO 2 Depositing a conductive oxide on the outer surface of the positive electrode composite particles of the lithium supplement additive, wherein the conductive oxide comprises In 2 O 3 、ZnO、SnO 2 Forming an encapsulating conductive oxide layer.
In some embodiments, the ion conductor encapsulation layer can enhance the ionic conductivity of the positive electrode composite material, thereby enhancing the ionic conductivity of the positive electrode composite material and facilitating the outward transport of lithium ions of the positive electrode composite material. The material for preparing the ion conductor encapsulation layer comprises at least one of perovskite type, NASICON type, garnet type or polymer type solid electrolyte; the thickness of the ion conductor packaging layer is 5-200nm; the method and conditions for forming the ion conductor encapsulating layer are specifically formed in accordance with the method for forming a perovskite-type, NASICON-type, garnet-type or polymer-type solid electrolyte.
In some embodiments, the method of preparing the positive electrode composite material includes the steps of:
s11, adding NiCO 3 、Ni(OH) 2 NiO, liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one lithium source and the anode active material are dissolved in anhydrous solvents such as absolute ethyl alcohol, methanol, acetone and the like, and then are stirred for 2 to 6 hours at the temperature of 80 to 100 ℃ to obtain a composite precursor;
s21, keeping the temperature of the composite precursor at 400-500 ℃ for 2-6 hours, heating to 680-780 ℃ and keeping the temperature for 12-24 hours to obtain the core-shell structure cathode composite material, wherein the shell layer is Li 2 NiO 2 Lithium supplement additive, wherein the inner core is a positive active material;
and S31, after the positive electrode composite material with the core-shell structure is obtained, forming at least one of an isolation packaging layer, an ion conductor packaging layer and an electronic conductor packaging layer on the outer surface of the shell layer.
Correspondingly, a second aspect of the embodiments of the present application provides a positive electrode composite material, which is a core-shell structure and includes a positive electrode active material core and a lithium supplement additive shell layer in situ coated on an outer surface of the core, where the lithium supplement additive shell layer is made of a lithium source and a nickel source.
The cathode composite material provided by the second aspect of the embodiment of the application is of a core-shell structure and comprises a cathode active material core and a lithium supplement additive shell layer which is coated on the outer surface of the core in situ; on one hand, the shell layer is coated on the outer surface of the core in situ and is tightly combined with the anode active material, the lithium supplement additive is uniformly dispersed, and the lithium supplement effect is stable; on the other hand, the lithium supplement additive in the shell layer can effectively make up active lithium ions consumed by the formation of an SEI film during the first charge and discharge of the battery, so that the initial capacity is improved, and the energy density of the battery is further improved.
The embodiments of the present application can be prepared by the methods of the above embodiments.
In some embodiments, the nickel source is selected from: niCo 3 、Ni(OH) 2 And NiO. In some embodiments, the lithium source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of (a). These lithium and nickel sources can form Li by subsequent calcination treatment 2 NiO 2 The lithium supplement additive has a lower charging platform ratio and a good lithium supplement effect, and can provide charge/Li for charge compensation on a negative electrode + 。
In some embodiments, the lithium supplement additive shell made from a lithium source and a nickel source is Li 2 NiO 2 (ii) a The positive active material inner core comprises nickel cobalt lithium manganate and/or nickel cobalt lithium aluminate; and forming the nickel-rich ternary cathode material. The charge plateau of the lithium supplement additive is relatively low, specifically at 3.5V (vs. Li/Li) + ) When decomposed with the transition from crystalline to amorphous phase; and the decomposed amorphous phase provides a delithiation capacity of not less than 360mAh/g at the first charge, so that Li 2 NiO 2 The lithium supplement additive has good lithium supplement effect and can provide charge/Li for charge compensation on the negative electrode + . Meanwhile, the nickel source in the lithium supplement additive and the nickel source in the ternary anode material can play a role in synergy, and the reversible discharge specific capacity of the anode composite material is improved.
In some embodiments, the lithium supplement additive shell layer has a thickness of 5 to 50nm. In some embodiments, the lithium supplement additive shell layer in the positive electrode composite material is 1-10% by mass. If the thickness of the shell layer is too thick or the mass percentage content is too high, the gram capacity of the positive electrode composite material can be reduced because lithium ions in the lithium supplement additive do not participate in lithium circulation in the charging and discharging processes of the battery basically, and the energy density of the battery is reduced; if the shell layer is too thin or the mass percentage content is too low, the lithium supplementing effect of the lithium supplementing additive shell layer on the positive electrode composite material is poor, and lithium ions lost by the formed SEI film are difficult to compensate, so that the first effect of the positive electrode composite material is not improved, and the energy density of a battery is not improved.
In some embodiments, the outer surface of the lithium supplement additive shell layer further comprises at least one of an isolation encapsulation layer, an ion conductor encapsulation layer, and an electron conductor encapsulation layer. The isolation packaging layer can effectively isolate moisture, oxygen and the like from contacting with the lithium supplement additive in the positive electrode composite material to damage the material property, the stability of the positive electrode composite material is improved, the stable lithium supplement effect is realized, and the electrochemical performance of the positive electrode material is stabilized. The ion conductor packaging layer and the electron conductor packaging layer can improve the electron and ion conduction performance of the positive electrode composite material and improve the lithium extraction in the charging process.
In a third aspect of the embodiments of the present application, a positive electrode sheet is provided, and the positive electrode sheet includes the positive electrode composite material prepared by the above method, or includes the positive electrode composite material.
The positive plate provided by the third aspect of the embodiment of the present application includes the positive electrode composite material, and the positive electrode composite material is a core-shell structure and includes a positive electrode active material core and a lithium supplement additive shell layer in which the lithium supplement additive shell layer is in situ coated on an outer surface of the core. The lithium supplement additive has good lithium supplement capacity, the shell layer of the lithium supplement additive is tightly combined with the positive active material, the lithium supplement additive is uniformly dispersed, the lithium supplement effect is stable, active lithium ions consumed by the formation of an SEI (solid electrolyte interphase) film during the first charge and discharge of the battery can be effectively compensated, and the energy density of the battery is improved.
In some embodiments, the positive electrode current collector includes, but is not limited to, any one of a copper foil, an aluminum foil.
In some embodiments, the positive active layer further includes a conductive agent, a binder, and other components, and the materials are not particularly limited in this application, and may be selected according to the actual application requirement.
In some embodiments, the binder is present in the positive active layer in an amount of 2wt% to 4wt%. In particular embodiments, the binder may be present in an amount of 2wt%, 3wt%, 4wt%, and the like, which are typical and not limiting. In a specific embodiment, the binder comprises one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene butadiene rubber, hydroxypropyl methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.
In some embodiments, the content of the conductive agent in the positive electrode active layer is 3wt% to 5wt%. In specific embodiments, the content of the conductive agent may be 3wt%, 4wt%, 5wt%, and the like, which are typical, but not limiting, contents. In particular embodiments, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fibers, C60, and carbon nanotubes.
In some embodiments, the positive electrode sheet is prepared by the following steps: mixing the positive electrode composite material, the conductive agent and the binder to obtain electrode slurry, coating the electrode slurry on a current collector, and drying, rolling, die cutting and the like to obtain the positive electrode plate.
A fourth aspect of the embodiments of the present application provides a secondary battery including the positive electrode sheet described above.
The secondary battery provided by the fourth aspect of the embodiment of the application comprises the positive plate, and the positive plate comprises the positive composite material which takes the positive active material as the core and the lithium supplement additive shell layer coated on the outer surface of the core in situ, so that active lithium ions consumed by the battery due to the formation of the SEI film during the first charging can be effectively compensated, the gram capacity of the positive plate is effectively maintained, and the capacity retention rate of the positive plate is improved. Therefore, the secondary battery provided by the embodiment of the application has high energy density and good capacity retention rate.
The secondary battery of the embodiment of the present application may be a lithium ion battery or a lithium metal battery.
The negative electrode sheet, the electrolyte, the diaphragm and the like of the secondary battery in the embodiment of the present application are not particularly limited, and can be applied to any battery system.
In order to make the above implementation details and operations of the present application clearly understood by those skilled in the art, and to make the advanced performances of the positive electrode composite material and the preparation method thereof, the positive electrode sheet, and the secondary battery of the embodiments of the present application obviously manifest, the above technical solutions are exemplified by a plurality of embodiments.
Example 1
A positive electrode composite material, the preparation of which comprises the steps of:
(1) according to Li 2 NiO 2 The stoichiometric ratio of LiOH lithium source and NiCO 3 The nickel source, along with the NCM811 positive electrode active material, was dissolved in absolute ethanol and then heated at 80 deg.CStirring for 5 hours under the condition of (1) to obtain a composite precursor;
(2) keeping the temperature of the composite precursor at 400 ℃ for 6 hours, heating to 780 ℃ at the speed of 5 ℃/min, and keeping the temperature for 24 hours to obtain the core-shell structure cathode composite material, wherein the shell layer is Li 2 NiO 2 And the lithium supplement additive comprises a core which is a positive active material, wherein the mass ratio of a shell layer is 5wt%.
A lithium ion battery prepared by the steps of:
(3) preparing a positive plate: mixing the positive electrode composite material with SP: mixing PVDF in a mass ratio of 95; the rotation speed is set to 30Hz: respectively preparing the anode plates by homogenizing, coating, drying and cutting, and baking the anode plates in a vacuum oven at 100 ℃ to remove trace water;
(4) and (3) negative plate: lithium metal sheet with a diameter of 16 mm;
(5) electrolyte solution: 1mol/L LiPF 6 The solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) according to the volume ratio of 1:1;
(6) a diaphragm: a polypropylene microporous membrane;
(7) assembling the lithium ion battery: and assembling the lithium ion battery in an inert atmosphere glove box according to the assembling sequence of the lithium metal sheet, the diaphragm, the electrolyte and the positive plate.
Example 2
A positive electrode composite material, the preparation of which comprises the steps of:
(1) according to Li 2 NiO 2 Is expressed in terms of the stoichiometric ratio of LiNO 3 Lithium source and Ni (OH) 2 A nickel source and an NCM622 positive electrode active material are dissolved in absolute ethyl alcohol, and then the mixture is stirred for 5 hours at the temperature of 80 ℃ to obtain a composite precursor;
(2) keeping the temperature of the composite precursor at 400 ℃ for 6 hours, heating to 780 ℃ at the speed of 5 ℃/min, and keeping the temperature for 24 hours to obtain the core-shell structure cathode composite material, wherein the shell layer is Li 2 NiO 2 And the lithium supplement additive comprises a core which is a positive active material, wherein the mass ratio of a shell layer is 5wt%.
A lithium ion battery, prepared according to reference example 1, except that: the positive electrode composite material prepared in example 2 was used.
Example 3
A positive electrode composite material, the preparation of which comprises the steps of:
(1) according to Li 2 NiO 2 Stoichiometric ratio of C 6 H 5 Li 3 O 7 Dissolving a lithium source and a NiO nickel source and a nickel cobalt lithium aluminate anode active material in absolute ethyl alcohol, and then stirring for 5 hours at the temperature of 80 ℃ to obtain a composite precursor;
(2) keeping the temperature of the composite precursor at 400 ℃ for 6 hours, heating to 780 ℃ at the speed of 5 ℃/min, and keeping the temperature for 24 hours to obtain the core-shell structure cathode composite material, wherein the shell layer is Li 2 NiO 2 And the lithium supplement additive comprises a core which is a positive active material, wherein the mass ratio of a shell layer is 5wt%.
A lithium ion battery, prepared according to reference example 1, except that: the positive electrode composite material prepared in example 3 was used.
Example 4
A positive electrode composite material, which is different from example 1 in that: the mass ratio of the shell layer in the positive electrode composite material prepared in the step (2) is 1wt%.
A lithium ion battery, prepared according to reference example 1, except that: the positive electrode composite material prepared in example 4 was used.
Example 5
A positive electrode composite material, which is different from example 1 in that: the mass ratio of the shell layer in the anode composite material prepared in the step (2) is 10wt%.
A lithium ion battery, prepared according to reference example 1, except that: the positive electrode composite material prepared in example 5 was used.
Example 6
A positive electrode composite material, which is different from example 1 in that: the mass ratio of the shell layer in the positive electrode composite material prepared in the step (2) is 11wt%.
A lithium ion battery, prepared according to reference example 1, except that: the positive electrode composite material prepared in example 6 was used.
Comparative example 1
A lithium ion battery comprises the following preparation steps:
(1) preparing a positive plate: mixing Li 2 NiO 2 And an NCM811 positive electrode active material at a mass ratio of 5: mixing PVDF in a mass ratio of 95; the rotation speed is set to 30Hz: respectively preparing the anode plates by homogenizing, coating, drying and cutting, and baking the anode plates in a vacuum oven at 100 ℃ to remove trace water;
(2) and (3) negative plate: lithium metal sheet with a diameter of 16 mm;
(3) electrolyte: 1mol/L LiPF 6 The solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) according to the volume ratio of 1:1;
(4) a diaphragm: a polypropylene microporous membrane.
(5) Assembling the lithium ion battery: and assembling the lithium ion battery in an inert atmosphere glove box according to the assembling sequence of the lithium metal sheet, the diaphragm, the electrolyte and the positive plate.
Comparative example 2
A lithium ion battery comprises the following preparation steps:
(1) preparing a positive plate: mixing NCM811 positive electrode active material with SP: mixing PVDF in a mass ratio of 95; the rotation speed is set to 30Hz: respectively preparing the anode plates by homogenizing, coating, drying and cutting, and baking the anode plates in a vacuum oven at 100 ℃ to remove trace water;
(2) and (3) negative plate: lithium metal sheet with a diameter of 16 mm;
(3) electrolyte solution: 1mol/L LiPF 6 The solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) according to the volume ratio of 1:1;
(4) a diaphragm: a polypropylene microporous membrane;
(5) assembling the lithium ion battery: and assembling the lithium ion battery in an inert atmosphere glove box according to the assembling sequence of the lithium metal sheet, the diaphragm, the electrolyte and the positive plate.
Comparative example 3
A lithium ion battery comprises the following preparation steps:
(1) preparing a positive plate: mixing NCM622 positive electrode active material with SP: mixing PVDF in a mass ratio of 95; the rotation speed is set to 30Hz: respectively preparing the anode plates by homogenizing, coating, drying and cutting, and baking the anode plates in a vacuum oven at 100 ℃ to remove trace water;
(2) and (3) negative plate: lithium metal sheet with a diameter of 16 mm;
(3) electrolyte solution: 1mol/L LiPF 6 The solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) according to the volume ratio of 1:1;
(4) diaphragm: a polypropylene microporous membrane;
(5) assembling the lithium ion battery: and assembling the lithium ion battery in an inert atmosphere glove box according to the assembling sequence of the lithium metal sheet, the diaphragm, the electrolyte and the positive plate.
Further, to verify the improvement of the examples of the present application, the following electrochemical performance tests were performed on the CR2025 button cells assembled in examples 1 to 6 and comparative examples 1 to 3 by using a CT2001A LAND cell tester under the following test conditions: charging to 4.3V at 1C multiplying power constant current and constant voltage, and stopping current at 0.01C; and standing for 5min, and discharging to 2.75V at 1C multiplying power by constant current. The test results are shown in table 1 below:
TABLE 1
From the above test results, in example 1, by 5wt% Li 2 NiO 2 The battery made of the core-shell cathode composite material formed by the lithium supplement additive and the NCM811 has the first charge gram capacity of 219.5mAh/g, the first discharge gram capacity of 198mAh/g and the first effect of 90.2 percent; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 400mAh/g, and the first charge gram capacity of the anode is improved by 9.5mAh/g. Example 2, by 5wt% Li 2 NiO 2 The first charge gram capacity of the battery made of the core-shell cathode composite material formed by the lithium supplement additive and the NCM622 is 191mAh/g, the first discharge gram capacity is 163mAh/g, and the first effect is 85mAh/g3 percent; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 400mAh/g, and the first charge gram capacity of the anode is improved by 11mAh/g. Example 3, by 5wt% Li 2 NiO 2 The first charge gram capacity of a battery made of the core-shell cathode composite material formed by the lithium supplement additive and the nickel cobalt lithium aluminate is 218.5mAh/g, the first discharge gram capacity is 194.5mAh/g, and the first effect is 89.0%; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 400mAh/g, and the first charge gram capacity of the anode is improved by 9.5mAh/g. Example 4 by 1wt% Li 2 NiO 2 The first charge gram capacity of a battery made of the core-shell cathode composite material formed by the lithium supplement additive and the NCM811 is 211.9mAh/g, the first discharge gram capacity is 189.7mAh/g, and the first effect is 89.5%; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 400mAh/g, and the first charge gram capacity of the anode is improved by 1.9mAh/g. Example 5, 1wt% Li 2 NiO 2 The first charge gram capacity of a battery made of the core-shell cathode composite material formed by the lithium supplement additive and the NCM811 is 218.6mAh/g, the first discharge gram capacity is 195.9mAh/g, and the first effect is 89.6 percent; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 296mAh/g, and the first charge gram capacity of the positive electrode is improved by 8.6mAh/g. Example 6 by 11wt% Li 2 NiO 2 The first charge gram capacity of a battery made of the core-shell cathode composite material formed by the lithium supplement additive and the NCM811 is 218.3mAh/g, the first discharge gram capacity is 195.4mAh/g, and the first effect is 89.5%; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 285mAh/g, and the first charge gram capacity of the positive electrode is improved by 8.3mAh/g. Therefore, the lithium supplement additive is uniformly and stably coated on the surface of the positive active material while the lithium supplement additive is prepared, so that the process is simplified, and in the positive composite material with the core-shell structure, the lithium supplement additive and the positive active material are stably combined and uniformly distributed, so that active lithium ions consumed by the battery due to SEI film formation during first charging and discharging can be effectively compensated, the initial capacity of the battery is improved, and the cycle stability of the battery is improved.
However, in comparative example 1, li was directly added 2 NiO 2 Mixing with NCM811 positive electrode active material according to the mass ratio of 5The first charge gram capacity of the mixture is 216.5mAh/g, the first discharge gram capacity is 193.5mAh/g, and the first effect is 89.4 percent; wherein Li 2 NiO 2 The gram capacity of the lithium supplement additive is 340mAh/g, and the first charge gram capacity of the anode is improved by 7.5mAh/g. In comparative example 2, the NCM811 cathode active material was 95% in the first charge gram capacity of 210mAh/g, the first discharge gram capacity of 190mAh/g, and the first effect of 90.5%. In proportion 3, 95% of the NCM622 positive electrode active material was found to have a first charge gram capacity of 180mAh/g, a first discharge gram capacity of 153mAh/g and a first effect of 85.0%. It is apparent that comparative example 1 forms a positive electrode composite material by directly mixing a lithium supplement additive with a positive electrode active material, and the first effect and lithium supplement effect of the battery made are significantly lower than those of examples 1 to 6. While comparative examples 2 and 3 did not have the lithium supplement additive added, the capacity could not be increased.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. The preparation method of the positive electrode composite material is characterized by comprising the following steps of:
dissolving a lithium source, a nickel source and a positive active material in an anhydrous solvent, mixing and drying to coat the surface of the positive active material with the lithium source and the nickel source to obtain a composite precursor;
and calcining the composite precursor to obtain the cathode composite material with a core-shell structure, wherein the core of the cathode composite material is a cathode active material, and the shell of the cathode composite material is a lithium supplement additive.
2. The method of preparing a positive electrode composite material according to claim 1, wherein the nickel source is selected from the group consisting of: niCo 3 、Ni(OH) 2 At least one of NiO and NiO;
and/or, the lithium source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of (1).
3. The method for preparing the positive electrode composite material according to claim 2, wherein the positive electrode material is at least one selected from the group consisting of lithium iron phosphate, lithium cobaltate, lithium manganese iron phosphate, lithium manganate, lithium nickel cobalt aluminate, and lithium nickel manganate;
and/or, the anhydrous solvent is selected from: at least one of absolute ethyl alcohol, methanol and acetone.
4. The method of preparing a positive electrode composite material according to claim 3, wherein the lithium supplement additive is Li 2 NiO 2 (ii) a The positive electrode material comprises nickel cobalt lithium manganate and/or nickel cobalt lithium aluminate;
and/or the mass percentage of the shell layer of the lithium supplement additive in the positive electrode composite material is 1-10%.
5. The method for producing a positive electrode composite material according to any one of claims 1 to 4, wherein the conditions of the mixed drying treatment include: stirring for 2-6 hours at the temperature of 80-100 ℃;
and/or the step of calcination treatment comprises: keeping the temperature of the composite precursor at 400-500 ℃ for 2-6 hours, heating to 680-780 ℃ and keeping the temperature for 12-24 hours;
and/or after the positive electrode composite material with the core-shell structure is obtained, forming at least one of an isolation packaging layer, an ion conductor packaging layer and an electronic conductor packaging layer on the outer surface of the shell layer.
6. The cathode composite material is characterized by being of a core-shell structure and comprising a cathode active material inner core and a lithium supplement additive shell layer coated on the outer surface of the inner core in situ, wherein the lithium supplement additive shell layer is made of a lithium source and a nickel source.
7. The positive electrode composite material of claim 6, wherein the nickel source is selected from the group consisting of: niCo 3 、Ni(OH) 2 At least one of NiO and NiO;
and/or, the lithium source is selected from: liOH and LiNO 3 、C 6 H 5 Li 3 O 7 At least one of;
and/or the thickness of the shell layer of the lithium supplement additive is 5-50 nm;
and/or the mass percentage of the lithium supplement additive shell layer in the positive electrode composite material is 1-10%.
8. The positive electrode composite material of claim 6 or 7, wherein the lithium supplement additive shell layer comprises Li 2 NiO 2 (ii) a The positive active material core comprises lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate;
and/or the outer surface of the lithium supplement additive shell layer further comprises at least one of an isolation packaging layer, an ion conductor packaging layer and an electron conductor packaging layer.
9. A positive electrode sheet comprising the positive electrode lithium supplement additive prepared by the method according to any one of claims 1 to 5, or comprising the positive electrode lithium supplement additive according to any one of claims 6 to 8.
10. A secondary battery comprising the positive electrode sheet according to claim 9.
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