CN117894945A - Composite positive electrode material, preparation method and application thereof - Google Patents
Composite positive electrode material, preparation method and application thereof Download PDFInfo
- Publication number
- CN117894945A CN117894945A CN202410050026.0A CN202410050026A CN117894945A CN 117894945 A CN117894945 A CN 117894945A CN 202410050026 A CN202410050026 A CN 202410050026A CN 117894945 A CN117894945 A CN 117894945A
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- positive electrode
- electrode active
- lithium
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- 230000000977 initiatory effect Effects 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 229910000155 iron(II) phosphate Inorganic materials 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- NPFOYSMITVOQOS-UHFFFAOYSA-K iron(III) citrate Chemical compound [Fe+3].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NPFOYSMITVOQOS-UHFFFAOYSA-K 0.000 description 1
- SDEKDNPYZOERBP-UHFFFAOYSA-H iron(ii) phosphate Chemical compound [Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O SDEKDNPYZOERBP-UHFFFAOYSA-H 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 229940071264 lithium citrate Drugs 0.000 description 1
- WJSIUCDMWSDDCE-UHFFFAOYSA-K lithium citrate (anhydrous) Chemical compound [Li+].[Li+].[Li+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O WJSIUCDMWSDDCE-UHFFFAOYSA-K 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
- 229910001947 lithium oxide Inorganic materials 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- PSACBMCCZLGPIA-UHFFFAOYSA-J molybdenum(4+) tetraformate Chemical compound C(=O)[O-].[Mo+4].C(=O)[O-].C(=O)[O-].C(=O)[O-] PSACBMCCZLGPIA-UHFFFAOYSA-J 0.000 description 1
- CZDSWLXAULJYPZ-UHFFFAOYSA-J molybdenum(4+);dicarbonate Chemical compound [Mo+4].[O-]C([O-])=O.[O-]C([O-])=O CZDSWLXAULJYPZ-UHFFFAOYSA-J 0.000 description 1
- TXCOQXKFOPSCPZ-UHFFFAOYSA-J molybdenum(4+);tetraacetate Chemical compound [Mo+4].CC([O-])=O.CC([O-])=O.CC([O-])=O.CC([O-])=O TXCOQXKFOPSCPZ-UHFFFAOYSA-J 0.000 description 1
- GDXTWKJNMJAERW-UHFFFAOYSA-J molybdenum(4+);tetrahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[Mo+4] GDXTWKJNMJAERW-UHFFFAOYSA-J 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 239000006012 monoammonium phosphate Substances 0.000 description 1
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 239000005033 polyvinylidene chloride Substances 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000000661 sodium alginate Substances 0.000 description 1
- 235000010413 sodium alginate Nutrition 0.000 description 1
- 229940005550 sodium alginate Drugs 0.000 description 1
- CMZUMMUJMWNLFH-UHFFFAOYSA-N sodium metavanadate Chemical compound [Na+].[O-][V](=O)=O CMZUMMUJMWNLFH-UHFFFAOYSA-N 0.000 description 1
- 235000015393 sodium molybdate Nutrition 0.000 description 1
- 239000011684 sodium molybdate Substances 0.000 description 1
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- MHSKRLJMQQNJNC-UHFFFAOYSA-N terephthalamide Chemical compound NC(=O)C1=CC=C(C(N)=O)C=C1 MHSKRLJMQQNJNC-UHFFFAOYSA-N 0.000 description 1
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- 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
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application belongs to the technical field of battery materials, and particularly relates to a composite positive electrode material, and a preparation method and application thereof. The composite positive electrode material comprises positive electrode active particles and lithium supplementing particles dispersed on the surface of the positive electrode active material in a dot form. In the composite positive electrode material, the surface of the positive electrode active particles comprises lithium supplementing particles dispersed in a dot form, and the lithium supplementing particles are distributed on the surface of the positive electrode active material in a dot form, so that the lithium supplementing particles are beneficial to uniformly supplementing lithium to the positive electrode active material, the lithium supplementing effect of the lithium supplementing particles to the positive electrode active material is improved, and the electrochemical performance of the composite positive electrode material is improved.
Description
Technical Field
The application belongs to the technical field of battery materials, and particularly relates to a composite positive electrode material, and a preparation method and application thereof.
Background
In the process of charging and discharging the lithium ion battery, a large amount of solid electrolyte interface film, namely SEI film, is generated on the surface of the negative electrode of the battery, so that limited active lithium ions and electrolyte in the battery are consumed, and irreversible capacity loss is caused. And the process reduces the energy density and cycle life of the lithium ion secondary battery, limiting the application of the lithium ion battery. In the related art, by adding a lithium supplementing material into the positive electrode material, the first irreversible capacity loss of the lithium battery caused by active lithium ion loss can be effectively compensated.
In practical application, the lithium supplementing material is required to be stored independently, and the addition amount is required to be calculated in the processing process; in addition, the anode active material and the lithium supplementing additive are unevenly mixed in the homogenizing process; and the lithium supplementing additive can produce gas in the application process of the battery. Although the prior art has means for compounding the positive electrode active material and the lithium supplementing additive, it is still difficult to uniformly disperse and mix the lithium supplementing additive and the positive electrode active material. After simple compounding, the lithium supplementing additive in the composite material is easy to generate structural collapse in the lithium removing process, so that the problems of pole piece pits and the like are caused, the uniform lithium supplementing effect is affected, and the stability of the pole piece is reduced.
Therefore, how to improve the uniform lithium supplementing effect of the lithium supplementing additive on the positive electrode active material is still a key factor for improving the lithium supplementing effect and ensuring the electrochemical performance such as the stability of the pole piece.
Disclosure of Invention
The purpose of the application is to provide a composite positive electrode material, a preparation method and application thereof, and aims to solve the problem that the conventional lithium supplementing additive is poor in uniform lithium supplementing effect on a positive electrode active material to a certain extent.
In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:
In a first aspect, the present application provides a composite positive electrode material comprising positive electrode active particles and lithium supplementing particles dispersed in a punctiform form on the surface of the positive electrode active material.
In a second aspect, the present application provides a method for preparing a composite positive electrode material, including the steps of:
preparing positive electrode active particles;
and preparing lithium supplementing particles loaded in a dot form on the surface of the positive electrode active material to obtain the composite positive electrode material.
In a third aspect, the present application provides a secondary battery, where the positive electrode sheet of the secondary battery includes the composite positive electrode material described above or the composite positive electrode material prepared by the method described above.
The composite positive electrode material provided by the first aspect of the application comprises positive electrode active particles and lithium supplementing particles dispersed on the surface of the positive electrode active material in a punctiform form, so that the lithium supplementing particles are distributed on the surface of the positive electrode active material in a punctiform form, the phenomenon of uneven dispersion of lithium supplementing material powder which is independently added in a homogenizing process can be avoided, and the uniform lithium supplementing of the positive electrode active material is facilitated; and the problem of resistivity increase caused by coating the anode active material by the metal oxide remained after the lithium supplementing material is subjected to lithium removal is avoided. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
According to the preparation method of the composite positive electrode material, after positive electrode active particles are prepared, lithium supplementing particles loaded in a dot form are prepared on the surface of the positive electrode active material, and the composite positive electrode material is obtained. The lithium supplementing material is dispersed on the surface of the positive electrode active particles in a dot shape, so that the lithium supplementing material is beneficial to uniformly supplementing lithium to the positive electrode active material, the composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
The secondary battery provided by the third aspect of the application, because the positive plate comprises the composite positive electrode material with the characteristics of good structural stability, excellent lithium supplementing effect, high conductivity, good multiplying power performance, good circulation stability and the like, the stability, capacity, multiplying power performance, circulation performance and other electrochemical performances of the positive plate are improved, and the energy density, circulation stability and other electrochemical performances of the secondary battery are further improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly introduce the drawings that are needed in the embodiments or the description of the prior art, it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a composite positive electrode material according to an embodiment of the present application; wherein 1 is positive electrode active particles, 2 is lithium supplementing particles, 3 is a porous coating layer, and 4 is reducing particles;
fig. 2 is a schematic flow chart of a method for preparing a composite positive electrode material according to an embodiment of the present application;
fig. 3 is a scanning electron microscope image of the composite positive electrode material provided in example 1 of the present application.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, 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 for purposes of illustration only and are not intended to limit the present application.
In this application, the term "and/or" describes an association relationship of an association object, which means that there may be three relationships, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) 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, c may be single or multiple, respectively.
It should be understood that, in various embodiments of the present application, the sequence number of each process does not mean that the sequence of execution is sequential, and some or all of the steps may be executed in parallel or sequentially, where the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application in the examples 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 weights of the relevant components mentioned in the examples of the present application may refer not only to specific contents of the respective components but also to the proportional relationship between the weights of the respective components, and thus, it is within the scope of the disclosure of the examples of the present application as long as the contents of the relevant components are scaled up or down according to the examples of the present application. Specifically, the mass in the examples of the present application may be a mass unit known in the chemical industry such as μ g, mg, g, kg.
The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. 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 defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
A first aspect of the present embodiment provides a composite positive electrode material including positive electrode active particles 1 and lithium supplementing particles 2 dispersed in a dot form on the surface of the positive electrode active material.
The composite positive electrode material provided by the first aspect of the application comprises the positive electrode active particles 1 and the lithium supplementing particles 2 dispersed on the surface of the positive electrode active material in a punctiform form, so that the lithium supplementing particles 2 are distributed on the surface of the positive electrode active material 1 in a punctiform form, the phenomenon of uneven dispersion of the lithium supplementing material 2 powder independently added in the homogenizing process can be avoided, and the uniform lithium supplementing of the positive electrode active material 1 is facilitated; and the problem of resistivity increase caused by coating the anode active material with the metal oxide remained after the lithium supplementing material 2 is subjected to lithium removal is avoided. The composite uniformity and stability of the positive electrode active material 1 and the lithium supplementing material 2 are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
In some possible implementations, as shown in fig. 1, the composite cathode material includes a cathode active particle 1 and a porous coating layer 3 coated on the surface of the cathode active particle 1, and the lithium supplementing particle 2 is supported in the pores of the porous coating layer. The composite positive electrode material comprises positive electrode active particles 1 and a porous coating layer 3 coated on the surface of the positive electrode active particles 1, wherein lithium supplementing particles 2 are loaded in pores of the porous coating layer 3, so that the lithium supplementing particles 2 are distributed on the surface of the positive electrode active material in a punctiform manner through a pore structure in the porous coating layer 3, and the phenomenon of uneven dispersion of lithium supplementing material powder which is independently added in a homogenizing process can be avoided; and the problem of resistivity increase caused by coating the anode active material by the metal oxide remained after the lithium supplementing material is subjected to lithium removal is avoided. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved. In addition, the pore structure in the porous coating layer 3 coated on the surface of the positive electrode active particles 1 not only ensures that the lithium supplementing particles 2 are dispersed on the surface of the positive electrode active material in a dot shape, but also can be used as a lithium ion inlet and outlet passage, has good ion and electron conducting capacity, and improves the conductivity of the composite positive electrode material.
In some possible implementations, the morphology of the lithium-compensating particles 2 includes a sphere.
In some possible implementations, the lithium-compensating particles 2 are grown in situ in the pores of the porous coating layer 3; under the condition, the pore structure in the porous coating layer 3 can play a role in limiting the in-situ growth of the lithium supplementing particles 2, so that the lithium supplementing particles 2 are ensured to grow on the surface of the positive electrode active material in a dot-like dispersed manner, and the phenomenon of uneven dispersion of the lithium supplementing material powder which is independently added in the homogenizing process can be avoided; and the problem of resistivity increase caused by coating the anode active material by the metal oxide remained after the lithium supplementing material is subjected to lithium removal is avoided. The lithium supplementing effect of the composite positive electrode material is improved, and the conductivity of the composite positive electrode material is improved.
In some possible implementations, the porous coating layer 3 contains a carbon material, and the porous coating layer 3 of the carbon material has good ion and electron conducting capability and can improve the conductivity of the composite positive electrode material.
In some possible implementations, the carbon material includes at least one of amorphous carbon, carbon fiber, graphite, graphene. The porous coating layer 3 containing these carbon materials can ensure that the lithium-compensating particles 2 are grown on the surface of the positive electrode active material in a dot-like dispersed manner, and can also improve the electrical conductivity and structural stability of the composite positive electrode material.
In some possible implementations, the pores in the porous coating layer 3 are blind pores, forming a full coating for the positive electrode active particles 1. In this case, the pores in the porous coating layer 3 are blind pores, which connect the surface layer and the inner layer of the porous coating layer 3 without penetrating the entire porous coating layer 3, and at this time, the porous coating layer 3 forms continuous full coating on the positive electrode active particles 1, the surface of the positive electrode active particles 1 has no exposed area, and the lithium supplementing particles 2 loaded in the pores of the porous coating layer 3 cannot directly contact with the core positive electrode active particles 1.
In other possible implementations, the pores in the porous coating layer 3 include through holes, forming a discontinuous coating for the positive electrode active particles 1. In this case, the pores in the porous coating layer 3 include through holes, which means connecting the surface layer and the inner layer of the porous coating layer 3 and penetrating the entire porous coating layer 3, and may also include blind holes, when the porous coating layer 3 forms a discontinuous coating on the positive electrode active particles 1, the through hole regions of the porous coating layer 3 on the surface of the positive electrode active particles 1 do not form a coating.
In some possible implementations, the pores in the porous coating layer 3 include through-holes, at least part of the lithium-compensating particles 2 being brought into contact with the positive electrode active particles 1 through the through-holes in the porous coating layer 3; in this case, the lithium supplementing particles 2 can be more uniformly distributed in a dot shape, and the lithium supplementing effect can be improved.
In some possible implementations, the surface of the lithium-compensating particles 2 and the surface of the porous coating layer 3 are loaded with the reducing particles 4. In some embodiments, the reducing particles 4 are supported on the surface of the porous coating layer 3 facing away from the positive electrode active particles 1 (i.e., the outer surface), the pore inner surface of the porous coating layer 3, and/or the surface of the lithium-compensating particles 2. The reducing particles 4 may be grown on the surface of the lithium-compensating particles 2 in contact with air, on the surface of the lithium-compensating particles 2 in contact with the porous coating layer 3, or on the surface of the lithium-compensating particles 2 in contact with the positive electrode active particles 1. In the above embodiment of the application, the reducing particles 4 can capture active oxygen/oxygen free radicals generated in the charging and discharging process of the composite positive electrode material, so that the generation of oxygen is reduced, more lithium ion access channels are reserved, the stability and safety of the composite positive electrode material are improved, and the rate capability of the composite positive electrode material is also improved. And the heterogeneous edge structure at the boundaries of the positive electrode active particles 1, the lithium supplementing particles 2 and the carbon material plays a role in catalysis, and is beneficial to improving the ion deintercalation efficiency.
In some possible implementation manners, the structural schematic diagram of the composite positive electrode material is shown in fig. 1, and the composite positive electrode material comprises positive electrode active particles 1 and a porous coating layer 3 coated on the surface of the positive electrode active particles 1, wherein lithium supplementing particles 2 are grown in situ in pores of the porous coating layer 3, at least part of the lithium supplementing particles 2 are in contact with the positive electrode active particles 1 through holes in the porous coating layer 3, and reducing particles 4 are also grown on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3. In the composite positive electrode material of the embodiment of the application, the lithium supplementing particles 2 grow in situ in the pores of the porous coating layer 3, and the pore structure of the porous coating layer 3 plays a role in limiting the growth of the lithium supplementing particles 2, so that the lithium supplementing particles 2 are ensured to grow on the surface of the positive electrode active material in a dot-shaped dispersed manner. The phenomenon of uneven dispersion of the lithium supplementing material powder which is independently added in the homogenizing process can be avoided; and the problem of resistivity increase caused by coating the anode active material by the metal oxide remained after the lithium supplementing material is subjected to lithium removal is avoided. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved. The pore structure in the porous coating layer 3 can also be used as an in-out channel of lithium ions, has good ion and electron conducting capacity, and improves the conductivity of the composite anode material. In addition, the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 are also provided with the reducing particles 4, and the reducing particles 4 can capture active oxygen/oxygen free radicals generated in the charging and discharging process of the composite positive electrode material, so that the generation of oxygen is reduced, more lithium ion access channels are reserved, the stability and the safety of the composite positive electrode material are improved, and the rate capability of the composite positive electrode material is also improved. And the heterogeneous edge structure at the boundaries of the positive electrode active particles 1, the lithium supplementing particles 2 and the carbon material plays a role in catalysis, and is beneficial to improving the ion deintercalation efficiency.
In some possible implementations, in the composite positive electrode material, the mass percentage of the positive electrode active particles 1 to the lithium supplementing particles 2 is (79.1-93.9)%: (0.5-10)%. Under the condition of the proportion, the composite positive electrode material has higher capacity and circulation capacity and better lithium supplementing effect, can effectively compensate the amount of active lithium ions consumed by the negative electrode due to formation of the SEI film, and improves the circulation stability of the composite positive electrode material. Illustratively, in the composite positive electrode material, the mass ratio of the positive electrode active particles 1 to the lithium-compensating particles 2 may be 79.1%:10%, 82.0%:7.1%, 85%:4%, 92%:0.8%, 93.9%:0.5% or the like, or (79.1 to 93.9)%: any value between (0.5 and 10)%, more preferably 90.+ -. 5%: 2+/-1.5 percent.
In some possible implementations, the mass percentage of the carbon material in the composite positive electrode material is 1% -10%. In this case, the content of the carbon material can form a completely coated porous coating layer 3 on the gap surface between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, thereby improving the ion and electron conducting ability of the composite positive electrode material and improving the conductivity of the composite positive electrode material. Illustratively, the mass percent of the carbon material in the composite positive electrode material may be 1%, 2%, 4%, 6%, 8%, 10%, etc.
In some possible implementations, the mass of the reducing particles 4 in the composite positive electrode material is 1.1 to 1.6 times the theoretical oxygen release amount of the lithium-compensating particles 2. In this case, the content of the reducing particles 4 can fix the gaseous oxygen into solid oxide, and sufficiently fix the oxygen removed by the lithium supplementing material; and the capacity of the composite positive electrode material is ensured. Illustratively, in the composite positive electrode material, the mass of the reducing particles 4 is 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, etc. or any value between 1.1 and 1.6 times the theoretical oxygen release amount of the lithium supplementing particles 2.
In some possible implementations, in the composite positive electrode material, the particle size D50 of the positive electrode active particles 1 is 2 μm to 20 μm; the positive electrode active material with the particle size is beneficial to improving the tap density of the composite positive electrode material. Illustratively, in the composite positive electrode material, the particle size D50 of the positive electrode active particles 1 may be 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 18 μm, 20 μm, or the like, or any value between 2 μm and 20 μm.
In some possible implementations, the particle size D50 of the lithium-compensating particles 2 in the composite positive electrode material is 0.1 μm to 1.0 μm. Under the condition, the particle size of the lithium supplementing particles 2 is smaller, and the particles are distributed on the surface of the positive electrode active material in a dot shape, so that the particles can be more uniformly combined on the surface of the positive electrode active material, a more omnibearing lithium supplementing effect is achieved, and the problem of resistivity increase caused by coating the positive electrode active material by residual metal oxide after lithium removal of the lithium supplementing material can be effectively avoided. Illustratively, in the composite positive electrode material, the particle size D50 of the lithium supplementing particles 2 may be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, or the like, or any value between 0.1 μm and 1.0 μm.
In some possible implementations, the particle size D50 of the reducing particles 4 in the composite positive electrode material is 0.01 μm to 1.0 μm. In this case, the reducing particles 4 have small particle diameters, and can be distributed on the surfaces of the lithium-compensating particles 2 and the porous coating layer 3 in a dot shape, so that oxygen extracted from the lithium-compensating material can be sufficiently fixed, and the influence on the ion conductivity of the composite positive electrode material after the reducing material is combined with oxygen can be reduced by the dot-like distribution relative to the complete coating. Illustratively, in the composite positive electrode material, the particle size D50 of the reducing particles 4 may be 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, or the like, or any value between 0.01 μm and 1.0 μm.
In some possible implementations, in the composite cathode material, the coating thickness of the porous coating layer 3 is 5nm to 500nm. Under the condition, the coating thickness of the carbon material is beneficial to improving the ion and electron conducting capacity of the composite positive electrode material, improving the conductivity of the composite positive electrode material, playing a role in limiting the growth of the lithium supplementing particles 2 and promoting the lithium supplementing particles 2 to grow on the surface of the positive electrode active material in a dot-shaped dispersing manner. For example, in the composite positive electrode material, the coating thickness of the porous coating layer 3 may be 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, or any value between 5nm and 500nm.
In some possible implementations, in the composite positive electrode material, the mass percentage of the positive electrode active particles 1 to the lithium supplementing particles 2 is (79.1-93.9)%: (0.5-10)%; the mass percentage of the carbon material is 1-10%; the mass of the reducing particles 4 is 1.1 to 1.6 times of the theoretical oxygen release amount of the lithium supplementing particles 2. In this case, the lithium supplementing particles 2 are distributed on the surface of the positive electrode active material in a dot shape, are uniformly and stably dispersed, can effectively compensate the loss of active lithium ions, and have good lithium supplementing effect. The carbon material forms a coating layer on the clearance surfaces between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, so that the lithium supplementing particles 2 are ensured to be grown on the surface of the positive electrode active material in a dot-shaped dispersion manner, and meanwhile, the ion and electron conducting capacity of the composite positive electrode material is improved. The reducing particles 4 are also distributed on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 in a punctiform manner, so that active oxygen/oxygen free radicals generated in the charging and discharging process of the composite positive electrode material can be captured in time, the generation of oxygen is reduced, and the stability, safety, rate capability and other electrochemical properties of the composite positive electrode material can be improved. And the heterogeneous edge structure at the boundaries of the positive electrode active particles 1, the lithium supplementing particles 2 and the carbon material plays a role in catalysis, and is beneficial to improving the ion deintercalation efficiency.
In some possible implementations, in the composite positive electrode material, the particle size D50 of the positive electrode active particles 1 is 2 μm to 20 μm; the granularity D50 of the lithium supplementing particles 2 is 0.1-1.0 mu m; the particle size D50 of the reducing particles 4 is 0.01 μm to 1.0 μm; the thickness of the porous coating layer 3 is 5nm to 500nm. In this case, the relationship between the particle size of the positive electrode active particles 1, the particle size of the lithium supplementing particles 2, the particle size of the reducing particles 4, the coating thickness of the porous coating layer 3, and other dimensions is fully ensured, the lithium supplementing particles 2 are uniformly and stably distributed on the surface of the positive electrode active material in a dotted manner, the reducing particles 4 are also distributed on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 in a dotted manner, and the carbon material forms the coating layer on the gap surfaces between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, so that the composite positive electrode material is ensured to have the advantages of good structural stability, excellent lithium supplementing effect, high conductivity, good rate capability, good cycle stability, and the like.
In some possible implementations, the material of the positive electrode active particles 1 includes LiCoO 2 、Li(Ni x1 Co x2 Mn x3 )O 2 、LiMn 2 O 4 、LiFePO 4 、LiMnPO 4 、LiMn i Fe 1-i PO 4 、Li 3 V 2 (PO4) 3 Wherein 0 < x1 < 1,0 < x2 < 1,0 < x3 < 1, and x1+x2+x3=1, 0 < i < 1. These positive electrode active particle 1 materials all have rich lithium ion storage sites, and can provide higher specific capacity. Meanwhile, the method has the characteristics of higher safety, long service life, strong adaptability, high energy density, low cost, long endurance mileage, good low-temperature performance and the like, and has wide application prospects in the field of new energy. By coating the surface of the positive electrode active material particles with the porous coating layer 3 and loading the lithium supplementing particles 2 in the pores of the porous coating layer 3, the lithium supplementing particles 2 are distributed in a dot shape, and the reducing particles 4 are grown on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3, the electronic conductivity, the ionic conductivity, the structural stability, the lithium supplementing effect, the rate performance, the cycling stability and other electrochemical performances of the composite positive electrode material can be remarkably improved.
In some possible implementations, the lithium-compensating particles 2 include a compound of the formula Li x M y O z Wherein 1 is<x<8，0.1<y<3，0<z<8, M comprises at least one transition metal element of iron, cobalt, zirconium, nickel and manganese. In this case, after the lithium-supplementing materials uniformly grow on the surface of the positive electrode active particles 1 to form dot-shaped distribution, the loss of lithium ions can be timely supplemented in the cyclic charge and discharge process of the composite positive electrode material. And the lithium supplementing materials have the advantages of low synthesis difficulty, high material stability, low lithium removal potential, high lithium supplementing capacity of the lithium supplementing agent per unit mass and the like.
In some possible implementations, the material of the reducing particles 4 includes at least one of magnesium, zinc, lead, copper, tin, ferrous sulfide, molybdenum sulfide, tin sulfide, argon copper sulfide, tungsten sulfide, cobalt sulfide. In this case, the material of the reducing particles 4 includes metals such as magnesium, zinc, lead, copper, and tin, which have reducing properties, and these metals grow on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3 in the form of particles of simple substance or alloy, and can timely capture oxygen radicals generated, thereby reducing gas generation. In addition, the material of the reducing particles 4 can also be metal sulfide, sulfur can be changed in valence, and the sulfur reacts with the generated active oxygen to generate solid elemental sulfur, so that the active oxygen is anchored, and the generated gas is prevented from negatively affecting the performance and the safety of the battery. In addition, the introduction of sulfur does not affect the performance of the composite positive electrode material, and the reducing material is distributed on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3 in a dot shape in a small particle form, so that the obstruction to the intercalation and deintercalation of lithium ions can be reduced relative to a full coating layer, and the electrochemical performance of the composite positive electrode material is ensured.
The composite positive electrode material of the above embodiment of the present application can be prepared by the method of the following embodiment.
In a second aspect, as shown in fig. 2, an embodiment of the present application provides a method for preparing a composite positive electrode material, including the following steps:
s10, preparing positive electrode active particles 1;
s20, preparing lithium supplementing particles 2 loaded in a dot form on the surface of the positive electrode active material 1 to obtain the composite positive electrode material.
According to the preparation method of the composite positive electrode material, after the positive electrode active particles 1 are prepared, lithium supplementing particles 2 loaded in a dot form are prepared on the surface of the positive electrode active material 1, and the composite positive electrode material is obtained. The lithium supplementing material 2 is dispersed on the surface of the positive electrode active particles 1 in a dot shape, so that the lithium supplementing material is beneficial to uniformly supplementing lithium to the positive electrode active material 1, the composite uniformity and stability of the positive electrode active material 1 and the lithium supplementing material 2 are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
In the above step S10, the positive electrode active particles 1 are prepared. In some possible implementations, the preparation steps of the positive electrode active particles 1 include: the raw material components are obtained according to the stoichiometric ratio of each element in the positive electrode active material, mixed and sintered in inert atmosphere to prepare the positive electrode active particles 1. The stoichiometric ratio of each element in the positive electrode active material may be a molar ratio, a mass ratio converted from the molar ratio, or the like.
In some possible implementations, the material of the positive electrode active particles 1 includes LiCoO 2 、Li(Ni x1 Co x2 Mn x3 )O 2 、LiMn 2 O 4 、LiFePO 4 、LiMnPO 4 、LiMn i Fe 1-i PO 4 、Li 3 V 2 (PO4) 3 Wherein 0 < x1 < 1,0 < x2 < 1,0 < x3 < 1, and x1+x2+x3=1, 0 < i < 1. In this case, the positive electrode active materials have good electrochemical properties. When the material of the positive electrode active particles 1 is the above material, raw material components to be prepared include a lithium source, a cobalt source, a nickel source, a molybdenum source, a manganese source, an iron source, a phosphorus source, a vanadium source, and the like.
In some possible implementations, the lithium source includes at least one of lithium oxide, lithium carbonate, lithium hydroxide, lithium acetate, lithium phosphate, lithium citrate.
In some possible implementations, the iron source includes one or more of ferric nitrate, ferrous sulfate, ferric citrate, ferrous oxalate, ferric oxide, ferrous phosphate.
In some possible implementations, the manganese source includes MnO 2 、Mn(NO 3 ) 2 、MnSO 4 、Mn 3 (PO 4 ) 2 ·3H 2 At least one of O.
In some possible implementations, the phosphorus source includes one or more of phosphoric acid, monoammonium phosphate, diammonium phosphate, lithium dihydrogen phosphate, iron phosphate.
In some possible implementations, the cobalt source includes at least one of cobalt sulfate, cobalt carbonate, cobalt nitrate, cobalt chloride.
In some possible implementations, the nickel source includes at least one of nickel sulfate, nickel carbonate, nickel nitrate, nickel chloride.
In some possible implementations, the molybdenum source includes at least one of molybdenum hydroxide, ammonium molybdate, sodium molybdate, molybdenum trioxide, molybdenum dioxide, molybdenum carbonate, molybdenum formate, molybdenum acetate.
In some possible implementations, the vanadium source includes at least one of vanadium trioxide, ammonium metavanadate, sodium metavanadate.
In some possible implementations, the step of loading the lithium supplementing particles 2 on the surface of the positive electrode active material 1 includes:
s21, preparing a porous coating layer 3 on the surface of the anode active particles 1 to obtain coated particles;
s22, preparing lithium supplementing particles 2 in the pores of the porous coating layer 3 to obtain the composite anode material.
According to the preparation method of the composite positive electrode material, after the positive electrode active particles 1 are prepared, the porous coating layer 3 is prepared on the surface of the positive electrode active particles 1, so that the porous structure of the porous coating layer not only has good ion and electron conducting capacity, but also can improve the conductivity of the positive electrode composite material, and the porous structure can provide a limiting effect for the lithium supplementing particles 2 for subsequent growth. And the lithium supplementing material is promoted to be dispersedly grown on the surface of the positive electrode active particles 1 in a dot shape under the limited domain effect of the porous coating layer 3. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
In the above step S21, the porous coating layer 3 is prepared on the surface of the positive electrode active particles 1. In some possible implementation manners, after the positive electrode active particles 1 are prepared, a porous coating layer 3 is prepared on the surface of the positive electrode active particles 1, and the porous coating layer 3 has good ion and electron conducting capability, so that not only can the conductivity of the positive electrode composite material be improved, but also the porous structure enables part of the surface of the positive electrode active particles 1 to be exposed in the air, and a domain limiting effect is provided for the lithium supplementing particles 2 for subsequent growth.
In some possible implementations, the preparation steps of the porous coating layer 3 include: after mixing the pore-forming agent, the organic carbon source and the positive electrode active particles 1, a first sintering treatment is performed under an inert atmosphere, and a porous coating layer 3 is formed on the surface of the positive electrode active particles 1. In this case, the organic carbon source and the pore-forming agent are uniformly coated on the surface of the positive electrode active particle 1 through the mixing process, and in the high temperature sintering process, the organic carbon source is converted into carbon materials such as amorphous carbon, carbon fiber, graphite, graphene and the like, which are coated on the surface of the positive electrode active particle 1, and the pore-forming agent generates gas in the carbonization process, so that pores are generated at corresponding positions on the surface of the positive electrode active particle 1, and the pore structure in the porous coating layer 3 formed on the surface of the positive electrode active particle 1 may be blind pores and/or through pores. When all the pores in the porous coating layer 3 are blind holes, forming full coating on the positive electrode active particles 1; when the pores in the porous coating layer 3 have through holes, the positions of the through holes expose the positive electrode active particles 1, thereby forming a discontinuous coating for the positive electrode active particles 1.
In some possible implementations, the mass ratio of the pore-forming agent, the organic carbon source, and the positive electrode active particles 1 is (1 to 5)%: (5-25)%: (70-94)%. Under the condition of the proportion, the organic carbon source can form a coating layer with uniform thickness on the surface of the positive electrode active particles 1 through high-temperature sintering treatment, and gas generated by the pore-forming agent in the carbonization process is enough to enable the porous coating layer 3 to form a full-coating or discontinuous-coating porous structure, and the pore distribution is uniform. Illustratively, in the mixture of the pore-forming agent, the organic carbon source, and the positive electrode active particles 1, the mass percentage of the pore-forming agent may be 1%, 2%, 3%, 4%, 5%, etc., the mass percentage of the organic carbon source may be 5%, 8%, 10%, 11%, 12%, 13%, 14%, 25%, etc., and the mass percentage of the positive electrode active particles 1 may be 70%, 75%, 78%, 82%, 84%, 85%, 86%, 88%, 94%, etc.
In some possible implementations, the pore-forming agent includes at least one of glycerol, urea, melamine, dicyandiamide; these pore formers can generate gas during carbonization, generate pores at corresponding positions, inhibit dense growth of the porous coating layer 3, and form the porous coating layer 3 on the surface of the positive electrode active particles 1.
In some possible implementations, the organic carbon source includes at least one of pitch, resin, oleylamine, oleic acid, cellulose, glucose; the organic carbon sources can be converted into carbon materials such as amorphous carbon, carbon fibers, graphite, graphene and the like in the high-temperature sintering process, and the carbon materials are coated on the surface of the positive electrode active particles 1. In addition, the porous coating layer 3 is formed on the surface of the positive electrode active particles 1 under the inhibition effect of the gas generated by the pore-forming agent.
In some possible implementations, the conditions of the first sintering process include: under the condition that the flow rate of the inert atmosphere is 300 ml/min-1000 ml/min, the temperature is raised to 600-700 ℃ at the speed of 2-5 ℃/min, and then the temperature is kept for 1-10 h. Under the sintering condition, the surface of the positive electrode active particles 1 can be coated with a carbon material such as amorphous carbon, carbon fiber, graphite, graphene, etc. by carbonizing an organic carbon source, and at the same time, the pore-forming agent can be carbonized to generate gas, thereby inhibiting the dense growth of the carbon layer and forming the porous coating layer 3 on the surface of the positive electrode active particles 1. Wherein, the inert atmosphere comprises nitrogen, argon, helium and the like, the air flow speed can be 300ml/min, 400ml/min, 500ml/min, 600ml/min, 700ml/min, 800ml/min, 900ml/min, 1000ml/min and the like, the heating rate can be 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min and the like, the heat preservation temperature can be 600 ℃, 620 ℃, 650 ℃, 680 ℃, 700 ℃ and the like, and the heat preservation time can be 1h, 2h, 3h, 4h, 5h, 8h, 10h and the like.
In some possible implementations, the pore size of the pores in the porous coating layer 3 is 0.1 μm to 1.0 μm. In this case, the pore diameter of the pores formed in the porous coating layer 3 is small, which provides a good confinement effect for the growth of the subsequent lithium supplementing particles 2, so that the particle diameter of the lithium supplementing particles 2 grown on the surface of the positive electrode active particles 1 is small and distributed uniformly. Illustratively, the pore size of the pores in the porous coating layer 3 may be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, etc.
In step S22 described above, the lithium-compensating particles 2 are prepared in the pores of the porous coating layer 3. In some possible implementations, the lithium-compensating particles 2 are bonded to the surface of the positive electrode active particles 1 through a through-hole structure in the porous coating layer 3; since the compatibility of the lithium supplementing material with the positive electrode active particles 1 is stronger than that of the carbon material, the lithium supplementing material generated in the preparation process can pass through the through holes in the porous coating layer 3, be preferentially combined on the surface of the positive electrode active particles 1, then gradually grow the lithium supplementing particles 2 to fill the through holes in the porous coating layer 3, and promote the lithium supplementing material to grow on the surface of the positive electrode active particles 1 in a dot-shaped dispersion manner under the limiting effect of the porous coating layer 3. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved.
In some possible implementations, the preparation steps of the lithium-compensating particles 2 include: after mixing the lithium source, the transition metal source and the particles coated by the porous coating layer 3, performing a second sintering treatment in an inert atmosphere, and depositing the generated lithium supplementing material in the pores of the porous coating layer 3 to form lithium supplementing particles 2. In this case, the lithium source and the transition metal source are sintered into the lithium supplementing material in the high-temperature inert atmosphere sintering process, the lithium supplementing material has strong compatibility with the positive electrode active particles 1, the lithium supplementing material passes through the through holes in the porous coating layer 3, is preferentially combined on the surface of the positive electrode active particles 1, then the lithium supplementing particles 2 are gradually grown to fill the pores of the through holes, and the lithium supplementing material is promoted to be dispersedly grown on the surface of the positive electrode active particles 1 in a dotted manner under the limiting effect of the porous coating layer 3. The composite uniformity and stability of the positive electrode active material and the lithium supplementing material are improved, the loss of active lithium ions can be more effectively compensated, and the lithium supplementing effect is improved. In addition, the method comprises the following steps. In the high-temperature sintering process, the grain structure of the positive electrode active particles 1 is further optimized, and the electrochemical performance is optimized.
In some possible implementations, the mass ratio of the lithium source, the transition metal source, and the coated particles is (0.08-1.55)%: (0.52-10.35)%: (88.10-99.40)%. Under the proportion, the lithium supplementing particles 2 are fully ensured to grow and fill in the pores of the porous coating layer 3 on the surface of the positive electrode active particles 1, and a composite coating effect is formed on the positive electrode active particles 1. Illustratively, the mass ratio of the lithium source, the transition metal source, and the coated particles may be 0.08%:0.52%:99.4%, 0.1%:1%:98.9%, 0.5%:5%:94.5%, 1%:6%:93%, 1.55%:10.35%:88.1%, etc.
In some possible implementations, the conditions of the second sintering process include: under the condition that the flow rate of inert atmosphere is 5 ml/min-200 ml/min, heating to 700-1000 ℃ at the speed of 1-10 ℃/min, and then preserving heat for 0.5-1 h. Under the sintering condition, the lithium source and the transition metal source can fully react to generate a lithium supplementing material, the lithium supplementing material is deposited in the pores of the porous coating layer 3, and the lithium supplementing particles 2 are gradually grown to fill the pores, and under the limited domain effect of the porous coating layer 3The lithium supplementing material is caused to grow in a dot-like dispersion on the surface of the positive electrode active particles 1. In some possible implementations, the lithium source includes LiOH, li 2 CO 3 、Li 2 O、Li 2 C 2 O 4 At least one of them.
In some possible implementations, the transition metal source includes an oxide and/or hydroxide of at least one transition metal element of iron, cobalt, zirconium, nickel, manganese.
In some possible implementations, the lithium-compensating particles 2 include a compound of the formula Li x M y O z Wherein 1 is<x<8，0.1<y<3，0<z<8, M comprises at least one transition metal element of iron, cobalt, zirconium, nickel and manganese. In this case, after the lithium-supplementing materials uniformly grow on the surface of the positive electrode active particles 1 to form dot-shaped distribution, the loss of lithium ions can be timely supplemented in the cyclic charge and discharge process of the composite positive electrode material.
In some possible implementations, the method further includes the step of preparing the reducing particles 4 on the surface of the lithium-compensating particles 2 and the surface of the porous coating layer 3: before and/or after the formation of the lithium-compensating particles 2, a vacuum vapor deposition is performed on the reducing metal and/or metal sulfide, and the reducing particles 4 are supported on the surface of the lithium-compensating particles 2 and the surface of the porous coating layer 3. In this case, the reducing particles 4 deposit a reducing substance such as a reducing metal or a metal sulfide by vacuum vapor deposition, and the reducing particles 4 are formed in a dot-like distribution on the surface of the porous coating layer 3 and the surface of the lithium-compensating particles 2. Wherein the reducing particles 4 may be prepared by deposition before the lithium supplementing particles 2 are prepared, and the deposited reducing particles 4 are distributed on the surface of the porous coating layer 3 and in the pores of the porous coating layer 3. And preparing lithium supplementing particles 2 on the basis of the preparation method to obtain the positive electrode material with the composite structure. In addition, the reducing particles 4 can be deposited and prepared after the lithium supplementing particles 2 are prepared, and the deposited reducing particles 4 are directly distributed on the surface of the porous coating layer 3 and then the lithium supplementing particles 2, so that the anode material with the composite structure is obtained. The reducing particles 4 may also be prepared by deposition before and after the preparation of the lithium-compensating particles 2. The capturing effect of the reducing particles 4 on oxygen free radicals is ensured, the gas generation is reduced, and the safety and stability of the material are improved.
In some embodiments, the step of preparing the reducing particles 4 comprises: and (3) placing the positive electrode material particles to be deposited into a physical vapor deposition instrument, taking one or more of magnesium, zinc, lead, copper, tin, ferrous sulfide, molybdenum sulfide, tin sulfide, argon copper sulfide, tungsten sulfide and cobalt sulfide as a target material, and depositing the target material on the surfaces of the small spherical positive electrode material particles to be deposited by vacuum evaporation to obtain the composite material with the dispersion anchoring of the reducing particles 4.
In some possible implementations, the material of the reducing particles 4 includes metals such as magnesium, zinc, lead, copper, tin, and the like with reducing property, and the metals grow on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3 in the form of particles of simple substance or alloy, so that generated oxygen free radicals can be captured timely, and gas generation is reduced. In addition, the material of the reducing particles 4 can also be metal sulfide, sulfur can be changed in valence, and the sulfur reacts with the generated active oxygen to generate solid elemental sulfur, so that the active oxygen is anchored, and the generated gas is prevented from negatively affecting the performance and the safety of the battery. In addition, the introduction of sulfur does not affect the performance of the composite positive electrode material, and the reducing material is distributed on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3 in a dot shape in a small particle form, so that the obstruction to the intercalation and deintercalation of lithium ions can be reduced relative to a full coating layer, and the electrochemical performance of the composite positive electrode material is ensured.
In some possible implementations, the total amount of reducing metal and/or metal sulphide to the mass percentage of particles to be loaded is (0.3-6.6)%: (93.4-99.7)%. Under the condition of the proportion, the reducing particles 4 can be uniformly distributed on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3, and the effect of reducing the gas production is fully ensured. Illustratively, the total amount of reducing metal and/or metal sulfide to the mass percent of particles to be loaded may be 0.3%:99.7%, 1% 99%, 2% 98%, 4% 96%, 6% 94%, 6.6% 93.4% and so on.
In some possible implementations, the conditions for vacuum vapor deposition include: vacuum degree of evaporation chamber is 10 -2 ～10 -6 Pa, the distance between the target and the base material is 1.0 cm-20 cm, the evaporation is regulated to 1-5 gears by a pressure regulator, the current is 10A-40A, and the residence time is 10S-60S. Under these conditions, the reducing material such as the reducing metal or the metal sulfide can be vaporized and gasified into particles having a predetermined energy, and uniformly deposited on the surfaces of the lithium-compensating particles 2 and the porous coating layer 3.
In some possible implementations, in the composite positive electrode material, the mass percentage of the positive electrode active particles 1 to the lithium supplementing particles 2 is (79.1-93.9)%: (0.5-10)%; the mass percentage of the carbon material is 1-10%; the mass of the reducing particles 4 is 1.1 to 1.6 times of the theoretical oxygen release amount of the lithium supplementing particles 2. In this case, the lithium supplementing particles 2 are distributed on the surface of the positive electrode active material in a dot shape, are uniformly and stably dispersed, can effectively compensate the loss of active lithium ions, and have good lithium supplementing effect. The carbon material forms a coating layer on the clearance surfaces between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, so that the lithium supplementing particles 2 are ensured to be grown on the surface of the positive electrode active material in a dot-shaped dispersion manner, and meanwhile, the ion and electron conducting capacity of the composite positive electrode material is improved. The reducing particles 4 are also distributed on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 in a punctiform manner, so that active oxygen/oxygen free radicals generated in the charging and discharging process of the composite positive electrode material can be captured in time, the generation of oxygen is reduced, and the stability, safety, rate capability and other electrochemical properties of the composite positive electrode material can be improved. And the heterogeneous edge structure at the boundaries of the positive electrode active particles 1, the lithium supplementing particles 2 and the carbon material plays a role in catalysis, and is beneficial to improving the ion deintercalation efficiency.
In some possible implementations, in the composite positive electrode material, the particle size D50 of the positive electrode active particles 1 is 2 μm to 20 μm; the granularity D50 of the lithium supplementing particles 2 is 0.1-1.0 mu m; the particle size D50 of the reducing particles 4 is 0.01 μm to 1.0 μm; the thickness of the porous coating layer 3 is 5nm to 500nm. In this case, the relationship between the particle size of the positive electrode active particles 1, the particle size of the lithium supplementing particles 2, the particle size of the reducing particles 4, the coating thickness of the porous coating layer 3, and other dimensions is fully ensured, the lithium supplementing particles 2 are uniformly and stably distributed on the surface of the positive electrode active material in a dotted manner, the reducing particles 4 are also distributed on the surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 in a dotted manner, and the carbon material forms the coating layer on the gap surfaces between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, so that the composite positive electrode material is ensured to have the advantages of good structural stability, excellent lithium supplementing effect, high conductivity, good rate capability, good cycle stability, and the like.
In a third aspect, an embodiment of the present application provides a secondary battery, where the positive electrode sheet includes the composite positive electrode material described above or the composite positive electrode material prepared by the method described above.
The secondary battery provided by the embodiment of the application has the advantages that the positive plate contains the composite positive electrode material with the characteristics of good structural stability, excellent lithium supplementing effect, high conductivity, good multiplying power performance, good circulation stability and the like, so that the stability, capacity, multiplying power performance, circulation performance and other electrochemical performances of the positive plate are improved, and the energy density, circulation stability and other electrochemical performances of the secondary battery are further improved.
The positive plate, the negative plate, the electrolyte, the diaphragm and the like in the secondary battery are not particularly limited, and the secondary battery can be suitable for any battery system.
In some possible implementations, the positive electrode sheet includes a current collector and an active layer formed on a surface of the current collector, where the active layer includes the composite positive electrode material described above or the composite positive electrode material prepared by the method described above. The active layer adopts the composite positive electrode material, and the composite positive electrode material has the characteristics of good structural stability, excellent lithium supplementing effect, high conductivity, good multiplying power performance, good cycling stability and the like, so that the stability, capacity, multiplying power performance, cycling performance and other electrochemical performances of the positive electrode sheet are improved.
In some possible implementations, the preparation of the active layer includes the steps of: and (3) mixing the composite anode material, the conductive agent and the binder to prepare electrode slurry, coating the electrode slurry on a current collector, and drying, rolling, die cutting and the like to prepare the anode plate.
In some possible implementations, the mass percentage of the composite positive electrode material in the active layer of the positive electrode sheet is 90% -95%. Specifically, the mass percentage of the coating-modified cathode material in the cathode active material layer may be 90%, 91%, 92%, 93%, 94%, 95%, or the like.
In some possible implementations, the current collector of the positive electrode sheet includes, but is not limited to, any one of copper foil, aluminum foil.
In some possible implementations, the binder is present in the positive electrode active material layer in an amount of 2wt% to 5wt%. In particular embodiments, the binder content may be a typical, but non-limiting, content of 2wt%, 3wt%, 4wt%, 5wt%, etc.
In some possible implementations, the binder includes one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan derivatives.
In some possible implementations, the content of the conductive agent in the positive electrode sheet active material layer is 1wt% to 5wt%. In specific embodiments, the content of the conductive agent may be a typical but non-limiting content of 3wt%, 4wt%, 5wt%, etc.
In some possible implementations, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes.
In some possible implementations, the negative electrode active material of the secondary battery includes, but is not limited to, graphite, soft carbon (e.g., coke, etc.), hard carbon, etc., carbon materials, or nitrides, tin-based oxides, tin alloys, nano-negative electrode materials, etc. Current collectors include, but are not limited to, any of copper foil, aluminum foil.
In some possible embodiments, the step of forming the negative electrode sheet includes: the negative electrode active material, conductive agents such as conductive carbon black, adhesives such as carboxymethyl cellulose and styrene-butadiene rubber, and solvents such as water are prepared into positive electrode mixed slurry according to the mass ratio of (80-99), 1-5, 2-10, 100, and then the positive electrode mixed slurry is subjected to vacuum defoamation, discharging, coating on a coating machine, rolling, slitting and die cutting to obtain the negative electrode plate.
In some possible implementations, the separator is capable of blocking the passage of electrons while allowing the passage of ions. Illustratively, the separator includes, but is not limited to, at least one material including polypropylene fibers, polyacrylonitrile fibers, polyvinyl formal fibers, poly (ethylene terephthalate), polyethylene terephthalate, polyamide fibers, poly (paraphenylene terephthalamide).
In some possible implementations, the electrolyte includes at least one soluble metal salt. In some embodiments, the metal salt comprises LiClO 4 、LiBF 4 、LiPF 6 、LiAsF 6 、LiCF 3 SO 3 、LiTDI、Li[(CF 3 SO 2 ) 2 N]、Li[(FSO 2 ) 2 N]、Li[(C m F 2m+1 SO 2 )(C n F 2n+1 SO 2 )N]Wherein m and n are natural numbers. The electrolyte can ensure high ion conductivity of the electrolyte, does not have harmful side reactions with electrode materials, electrolyte, diaphragms and the like, and has good chemical stability.
In some possible embodiments, the secondary battery includes at least one of a battery cell, a battery module, and a battery pack.
In some possible embodiments, the battery cell types include lithium ion batteries, as well as new types of batteries such as lithium air batteries, lithium metal batteries, and the like.
In some possible embodiments, the battery cells of the present application may be assembled into a battery module, and the number of the battery cells contained in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module. Further, the battery module may further include a case having an accommodating space in which the plurality of battery cells are accommodated.
In one possible embodiment, the battery cells and/or the battery modules may be further assembled into a battery pack, and the number of the battery cells or the battery modules included in the battery pack may be adjusted according to the application and the capacity of the battery pack.
In order that the implementation details and operations described above in the present application may be clearly understood by those skilled in the art, and that the advanced performances of the composite cathode material and the preparation method and application of the embodiment of the present application are significantly reflected, the technical solutions described above are exemplified by a plurality of embodiments below.
Example 1
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 2g of urea pore-forming agent, 85g of the anode active particles 1 prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 91.8 percent: 3.1%:5.1%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum vapor deposition is carried out for 40S under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and the reducing particles are deposited on the surfaces of the composite particles, namely, the lithium supplementing particles 2 and the porous particlesThe surface of the coating layer 3 grows reducing particles 4 to obtain a composite positive electrode material. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 90 percent: 3%:5%:2%.
Example 2
LiNi 0.8 Co 0.1 Mn 0.1 O 2 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: vacuum drying precursor powder Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 (100g) LiOH (28 g) is put into a planetary ball mill for ball milling for 5 hours and is evenly mixed. Heating at 5 deg.C/min in air (500 ml/min) atmosphere in a tube furnace, sintering at 700 deg.C for 10 hr, naturally cooling, pulverizing, and sieving with 200 mesh sieve to obtain LiNi 0.8 Co 0.1 Mn 0.1 O 2 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 2g of urea pore-forming agent, 85g of the anode active particles 1 prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 91.8 percent: 3.1%:5.1%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum vapor deposition is carried out for 40S under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and thenThe original particles are deposited on the surfaces of the composite particles, namely, the reducing particles 4 are grown on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3, so that the composite positive electrode material is obtained. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 90 percent: 3%:5%:2%.
Example 3
A LiCoO2 composite positive electrode material is prepared by the following steps:
(1) preparation of positive electrode active particles 1: anhydrous Co (NO) 3 ) 2 (182.9 g) and LiOH (26 g) were put into a planetary ball mill and ball-milled for 5h. Taking out the slurry, drying, grinding, heating at 5 deg.C/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 deg.C for 10h, naturally cooling, pulverizing, and sieving with 200 mesh sieve to obtain LiCoO 2 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 2g of urea pore-forming agent, 85g of the anode active particles 1 prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LCO and lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 91.8 percent: 3.1%:5.1%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum vapor deposition is carried out for 40S under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and the reducing particles are deposited on the surfaces of the composite particles, namely, the lithium supplementing particles 2 and the porous coating layer 3The surface of which grows reducing particles 4 to obtain the composite positive electrode material. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 90 percent: 3%:5%:2%.
Example 4
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 5g of urea pore-forming agent, 70g of anode active particles 1 prepared in the step (1) and 25g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 86.9%:3.0%:10.2%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum vapor deposition is carried out for 40S under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and the reducing particles are deposited on the surfaces of the composite particles, namely, the lithium supplementing particlesThe particles 2 and the porous coating layer 3 grow on the surface of the reducing particles 4 to obtain the composite positive electrode material. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 85.2 percent: 2.9%:10%:1.9%.
Example 5
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 1g of urea pore-forming agent, 70g of the anode active particles 1 prepared in the step (1) and 5g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 95.7 percent: 3.3%:1.0%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum vapor deposition is carried out for 40S under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and the reducing particles are deposited on the composite particlesThe surface of the lithium supplementing particles 2 and the surface of the porous coating layer 3 are grown with the reducing particles 4, and the composite positive electrode material is obtained. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 93.8 percent: 3.2%:1.0%:2.0%.
Example 6
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 2g of urea pore-forming agent, 70g of the anode active particles 1 prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 1.7g of lithium source LiOH and 3.3g of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 84.6 percent: 10.7%:4.7%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Vacuum deposition 130S is carried out under the conditions of Pa, 15cm distance of target substrate, 20A current and 1 gear, and thenThe original particles are deposited on the surfaces of the composite particles, namely, the reducing particles 4 are grown on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3, so that the composite positive electrode material is obtained. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 79.1 percent: 10%:4.4%:6.6%.
Example 7
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparation of positive electrode active particles 1: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer 3: uniformly mixing 2g of urea pore-forming agent, 70g of the anode active particles 1 prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer 3 formed on the surface of the anode active particles 1, wherein the pore size range of the porous coating layer subjected to detection discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles 2: 85mg of lithium source LiOH and 165mg of transition metal source Fe 2 O 3 And 100g of the porous coating layer 3 coated particles prepared in the step (2), after uniformly mixing, heating to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min, sintering for 2h, and growing Li at the non-continuous coated pore positions of the porous coating layer 3 5 FeO 4 Lithium supplementing particles 2, grinding after cooling to room temperature, and testing positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 94.2 percent: 0.5%:5.3%.
(4) Preparation of reducing particles 4: putting 10g of the composite particles prepared in the step (3) into a physical vapor deposition instrument, taking a reducing material FeS as a target material, and placing the composite particles in a range of 10 -2 Pa, 15cm distance of target material and base material, 20A current, and 1 gearAnd depositing 10S by vacuum evaporation, namely depositing the reducing particles on the surfaces of the composite particles, namely growing the reducing particles 4 on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3, so as to obtain the composite positive electrode material. In the detected composite positive electrode material, the mass ratio of the positive electrode active particles 1, the lithium supplementing particles 2, the porous coating layer 3 and the reducing particles 4 is 93.9 percent: 0.5%:5.3%:0.3%.
Comparative example 1
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparing positive electrode active particles: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer: uniformly mixing 2g of urea pore-forming agent, 85g of the positive electrode active particles prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain a discontinuous coated porous coating layer on the surface of the positive electrode active particles, wherein the pore size range of the discontinuous coated porous coating layer is 0.1-0.5 mu m after detection.
(3) Preparing lithium supplementing particles: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 After being uniformly mixed, the mixture is heated to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min for sintering for 2 hours, the mixture is ground and crushed after being cooled to room temperature, 100g of the carbon layer coated particles prepared in the process of the preparation method are added, ball milling is carried out for 1 hour, and the mixture is uniformly mixed to obtain the carbon layer coated LiFePO 4 Lithium supplementing agent Li 5 FeO 4 A composite material. Tested positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 91.8 percent: 3.1%:5.1%.
Comparative example 2
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparing positive electrode active particles: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethanol (100 ml) were put into a planetary ball mill for ball milling for 20 hours. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing a porous coating layer: uniformly mixing 2g of urea pore-forming agent, 85g of the positive electrode active particles prepared in the step (1) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the porous coating layer formed on the surface of the positive electrode active particles, wherein the pore size range of the porous coating layer subjected to discontinuous coating is 0.1-0.5 mu m.
(3) Preparing lithium supplementing particles: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 After being uniformly mixed, the mixture is heated to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min for sintering for 2 hours, the mixture is ground and crushed after being cooled to room temperature, 100g of porous coating layer coated particles prepared in the process of the preparation are added, ball milling is carried out for 1 hour, and the mixture is uniformly mixed to obtain carbon layer coated LFP and lithium supplementing agent Li 5 FeO 4 A composite material. Tested positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 And the mass ratio of the carbon layer is 91.8 percent: 3.1%:5.1%.
(4) Preparing a positive electrode composite material compounded by reductive particles: and (3) mixing 10g of the composite particles prepared in the step (3) with 0.2g of FeS particles, and carrying out ball milling for 1h to uniformly compound to obtain the composite anode material. Detected positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 The mass ratio of the carbon layer to the reducing particles is 90 percent: 3%:5%:2%.
Comparative example 3
LiFePO 4 The preparation of the composite positive electrode material comprises the following steps:
(1) preparing positive electrode active particles: anhydrous FePO 4 (150g)、C 6 H 12 O 6 (10g)、Li 2 CO 3 (46g) And absolute ethyl alcohol (100 ml)Ball milling in planetary ball mill for 20 hr. Taking out the slurry, drying, grinding, heating at 5 ℃/min under the protection of nitrogen (500 ml/min) in a tube furnace, sintering at 700 ℃ for 10 hours, naturally cooling, pulverizing, and sieving with a 200-mesh sieve to obtain LiFePO 4 Positive electrode active particles.
(2) Preparing lithium supplementing particles: 0.5g of lithium source LiOH and 1g of transition metal source Fe 2 O 3 After being evenly mixed, the mixture is heated to 800 ℃ at 2 ℃/min under the nitrogen atmosphere of 200ml/min for sintering for 2 hours, the mixture is ground and crushed after being cooled to room temperature, 95g of the mixture is added for preparation in the process of the preparation of the catalyst, the ball milling is carried out for 1 hour, and the LFP and the lithium supplementing agent Li are obtained after being evenly mixed 5 FeO 4 A composite material.
(3) Preparing a porous coating layer: uniformly mixing 2g of urea pore-forming agent, 85g of the anode active particles prepared in the step (2) and 13g of asphalt powder, heating to 600 at a speed of 2 ℃/min under the condition of 200ml/min of nitrogen flow rate, sintering for 1h, naturally cooling, and crushing to obtain the composite material with the porous coating layer discontinuously coated on the surface, wherein the pore size range of the porous coating layer discontinuously coated by detection is 0.1-0.5 mu m.
(4) Preparing a positive electrode composite material compounded by reductive particles: and (3) mixing 10g of the composite particles prepared in the step (3) with 0.2g of FeS particles, and carrying out ball milling for 1h to uniformly compound to obtain the composite anode material. Detected positive electrode active material LiFePO 4 Lithium supplementing agent Li 5 FeO 4 The mass ratio of the carbon layer to the reducing particles is 90 percent: 3%:5%:2%.
Further, to verify the advancement of the examples herein, the following performance tests were performed on the above examples and comparative examples, respectively:
1. Morphology Structure (SEM) analysis: SEM characterization is performed on the composite positive electrode material prepared in example 1, and the test result is shown in FIG. 3. It can be seen that a plurality of lithium supplementing particles 2 grow on the surface of the positive electrode material in example 1, a porous coating layer 3 is coated on the gap surface between the lithium supplementing particles 2 on the surface of the positive electrode active particles 1, and reducing particles 4 grow on the surfaces of the lithium supplementing particles 2 and the porous coating layer 3.
2. The sizes and contents of the positive electrode active particles 1, the lithium-compensating particles 2, and the reducing particles 4 in the composite positive electrode materials of examples and comparative examples were respectively tested, and the tap density, specific surface area, powder resistivity, and the like of the composite positive electrode material powder were tested, wherein,
(1) the relative content test method of the positive electrode active particles 1, the lithium supplementing particles 2, the coating layer 3 and the reducing particles 4 comprises the following steps: weigh a certain mass N 0 Soaking in quantitative and excessive 2mol/L hydrochloric acid solution at 90deg.C for 8 hr, ultrasonically washing the residue with deionized water to neutrality, collecting filtrate and residue, vacuum drying the residue at 130deg.C for 3 hr, and weighing to obtain N 3 The method comprises the steps of carrying out a first treatment on the surface of the Filtrate V 0 Elemental ion concentration C using ICP x Mass is calculated by the formula:
N x ＝V 0 *C x /M x *M y wherein M is x : molar mass M of the corresponding element y : the molar mass of the positive electrode active material, the lithium supplementing agent or the reducing substance corresponding to the element.
(2) The tap density testing method comprises the following steps: weighing the dried steel cylinder by using an analytical balance by using a refined JZ-1 powder tap density meter, and recording the weight m; filling a sample into a steel cylinder, weighing by an analytical balance, and recording the weight as M; covering a steel cap on the steel cylinder filled with the materials, putting the steel cap into a powder tap density meter, vibrating for 10min, wherein the frequency of the steel cap is fixed 60 times/second; taking out the steel cylinder measuring material deep l; tap density is calculated by the formula:
tap density= (M-M)/(L-L) ×pi R 2 Wherein, L: steel cylinder depth, R: the inner diameter of the steel cylinder.
(3) The specific surface area test method comprises the following steps: vacuum degassing is carried out for 30min at 300 ℃ before the sample testing, high-purity helium and nitrogen are turned on, the pressure is controlled at 0.16MPa, an instrument power switch is turned on sequentially after ventilation is carried out for about 3-5min, the system preheating is started, the flow preheating is regulated for 20-30min, after the preheating is finished, the airflow, the quantitative tube volume parameter, the sample name and the quality are filled, and the testing is started; the specific surface area is calculated by the formula:
surface area s=a m *n m *N A ，
1/[V*(P 0 /P-1)]＝1/V m *C+(C-1)/V m *C+P*(C-1)/(V m *C*P 0 )，
Wherein V: adsorbed gas volume, V m : single layer adsorbed gas capacity, C: constant, P/P 0 : relative pressure, n m : adsorption capacity of layer, n m ＝V m /22.414，N A ：6.022*10 23 。
(4) The powder resistivity test method comprises the following steps: the powder resistivity was tested using ST2742B of su lattice electrons, the test pressure was set to 6MPa, the gauge diameter D, the electrode distance L, and the test was started by clicking, and the powder resistivity of the material was directly read after the test was completed.
The test results are shown in table 1 below:
TABLE 1
From the above test results, it is clear that the higher the carbon coating mass ratio, the larger the specific surface area of the material, which is related to the soft carbon structure and low density of the coated carbon layer, the more the coating, the more pores and carbon fragments are brought by the soft carbon layer, thus resulting in a higher specific surface area and lower tap density. In addition, the soft carbon layer is made of conductive materials, so that higher coating layer ratio brings better conductive performance. It was also found from comparative example 3 that the formulation of the carbon coating after compounding resulted in a significant increase in specific surface area, and that similarly comparative example 3 also had a lower tap density than example 1, in relation to the formation of secondary particle agglomerates affecting the pores left inside after coating the carbon coating.
3. The composite positive electrode materials prepared in the above examples and comparative examples are applied to lithium ion batteries, and the specific preparation steps are as follows:
(1) Preparation of slurry, the composite cathode materials prepared in the above examples and comparative examples were respectively added in an agate ball milling pot with a volume of 500mL in 23.3g together with 0.12g of superconducting carbon black (SP) and 0.48g of binder polyvinylidene fluoride (PVDF), and then added with 16mg of solvent N-methylpyrrolidone (NMP), and ball milled for 4 hours at a rotational speed of 360rmp to prepare a slurry;
(2) Coating slurry, adjusting the scale of a scraper of a coater, uniformly coating the ball-milled slurry on an aluminum foil, placing the coated pole piece in a vacuum drying oven at 130 ℃ and baking for 3 hours;
(3) Rolling and punching, namely flatly placing the aluminum foil coated with the sizing agent in the middle of a rolling shaft, and rolling the polar plate; the front surface of the rolled pole piece is clung to the punching position, and the pole pieces are punched in sequence; the compaction density of the pole piece is controlled to be 2.0-2.4 g/cm < 3 >, the diameter is 14mm, and the thickness is 0.05-0.10 mm; placing the punched pole piece in a vacuum drying oven, and baking for 3 hours at the temperature of 130 ℃;
(4) And assembling the button cell, namely sequentially assembling the negative electrode shell, the elastic sheet, the steel sheet, the lithium sheet, the diaphragm, the positive electrode sheet and the positive electrode shell in a glove box, injecting 10 mu L of electrolyte in the process, and sealing the button cell by using a sealing machine, wherein the assembled button cell is used for subsequent electrochemical performance test.
The button cells prepared in each of the above examples and comparative examples were respectively tested for 0.1C discharge capacity, 1C cycle 100 times capacity retention rate, and unit composite material first-turn charge-discharge O 2 Yield, first effect, etc., test results are shown in table 2 below:
TABLE 2
From the above test results. Comparative example 1 and comparative example 1, the addition of the lithium supplement agent can significantly improve the 0.1C discharge capacity and the first effect because the addition of the lithium supplement agent supplements active lithium ions consumed by the formation of the SEI film during the first charge and discharge. In addition, the lithium supplementing agent at the outer side can remove lithium before the positive electrode active material of the inner core during the first-circle discharge, so that the lithium content of the positive electrode active material is not influenced while a high-quality SEI film is formed, and the higher-quality structure of the inner core shows higher capacity and higher retention in the subsequent 1C discharge processAnd the holding rate. From O 2 In terms of gas production, after addition of the reducing particles, the lithium supplement and O released by side reaction 2 The gas can be well fixed, so O measured in example 1 2 The gas production is low.
As can be seen from comparison of example 1, example 2 and example 3, the compounding scheme used in the examples of the present application has versatility in compounding different positive electrode active materials. The reason is that on one hand, the lithium-supplementing additive has lower lithium-removing potential than the positive active material core; on the other hand, the reducing particles, the lithium supplementing agent particles and the inert carbon layer play a role in protecting the inner core, so that the compounding stability of the inner core is improved. Furthermore, the reducing particles have better versatility for different positive electrode active particle cores and lithium supplementing agents, so that O 2 The gas production is relatively low.
As can be seen from comparison of examples 1, 4 and 5, on the premise of keeping the consistent mass ratio of the core, the lithium supplementing agent and the reducing particles, the mass ratio of the carbon layer is improved, which is favorable for obtaining a more complete coating of the inert layer and improving the cycle stability, but a thicker carbon layer provides higher requirements for the compactness of the surface layer, and because the density of the soft carbon layer is lower, more active lithium is consumed to form an SEI film, so that the initial effect is slightly reduced. Meanwhile, in a composite material of a unit mass, a higher carbon layer mass may result in a low content of the positive electrode active material, and thus may result in a decrease in gram capacity of the composite material, and conversely may increase the gram capacity of the composite material. Moreover, the higher inert carbon coating reduces the side reaction of the positive core material with the electrolyte, thus example 4 shows a relatively low O 2 Gas production.
From comparison of examples 1, 6 and 7, it can be seen that the improvement of the mass ratio of the lithium supplementing agent and the reducing particles is beneficial to the obvious improvement of the first effect. The reason is that more active lithium of the lithium supplementing agent can supplement active lithium lost due to generation of an SEI film in the first charge and discharge process. Meanwhile, the lithium supplementing agent is firstly delithiated to form an SEI film, so that lattice distortion caused by high delithiation of the inner core of the positive electrode active material is avoided, and higher circulation capacity is brought by the increase of the lithium supplementing agent and the reduction particles The quantity retention rate. However, the addition of too high a lithium supplementing agent and reducing particles results in a decrease in the ratio of the positive electrode active material per unit mass of the composite material, and the lithium supplementing agent does not have a cyclic reversible capacity, and thus, increasing the addition amount of the lithium supplementing agent and reducing particles results in a decrease in capacity. Conversely, the gram capacity of the composite material is increased, but the first effect and the cyclic capacity retention rate are reduced. Moreover, the increased amount of lithium supplement particles does not lead to more O 2 The gas generation amount is due to the fact that the synchronously increased reducing particles form more widely distributed O on the surface of the composite particles 2 A gas fixation site; while the reduced amount of lithium supplement particles causes O 2 A slight increase in gas production due to the small amount of reducing particle deposition resulting in weakened O 2 Effectiveness of the gas fixation site.
From the comparison of example 1 and comparative example 2, it can be found that the addition of the lithium supplement additive can partially improve the first effect, but because the addition of the oxygen scavenger is not captured, higher oxygen release is caused, and the release of oxygen can cause the surface impedance and polarization of the material to increase, thereby causing lower capacity and poorer cycle capacity retention.
As can be seen from comparison of example 1 and comparative example 3, the composite form of the composite material plays a critical role in the performance of the material, the reducing particles formed by vapor deposition of example 1 are smaller and more uniform, the capturing effect of the reducing agent on oxygen is better, therefore, the oxygen generation amount of example 1 is smaller, the side effect caused by gas generation during charging and discharging is smaller, and the composite material of comparative example 3 shows lower capacity and better first effect of better retention rate of circulating capacity.
The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.
Claims (12)
1. A composite positive electrode material is characterized by comprising positive electrode active particles and lithium supplementing particles dispersed on the surface of the positive electrode active material in a dot form.
2. The composite positive electrode material according to claim 1, further comprising a porous coating layer coated on the surface of the positive electrode active particles, wherein the lithium supplementing particles are supported in pores of the porous coating layer;
and/or, the morphology of the lithium supplementing particles comprises spherical shapes.
3. The composite positive electrode material of claim 2, wherein the lithium-compensating particles are grown in situ in the pores of the porous coating layer;
and/or the porous coating layer comprises a carbon material;
and/or the surfaces of the lithium supplementing particles and the porous coating layer are loaded with reducing particles;
and/or the pores in the porous coating layer are blind holes, so that the positive electrode active particles are fully coated;
Alternatively, the pores in the porous coating layer include through holes, forming a discontinuous coating for the positive electrode active particles.
4. The composite positive electrode material according to claim 3, wherein at least a portion of the lithium-compensating particles are in contact with the positive electrode active particles through the through-holes in the porous coating layer;
and/or the reducing particles are loaded on the surface of the porous coating layer, which faces away from the positive electrode active particles, the inner surface of the pores of the porous coating layer and/or the surface of the lithium supplementing particles.
5. The composite positive electrode material according to claim 3 or 4, wherein the mass percentage of the positive electrode active particles to the lithium-compensating particles is (79.1 to 93.9)%: (0.5-10)%;
and/or, in the composite positive electrode material, the mass percentage of the carbon material is 1% -10%;
and/or the mass of the reducing particles is 1.1-1.6 times of the theoretical oxygen release amount of the lithium supplementing particles;
and/or, in the composite positive electrode material, the particle size D50 of the positive electrode active particles is 2 μm to 20 μm; and/or the particle size D50 of the lithium supplementing particles is 0.1-1.0 mu m; and/or the particle size D50 of the reducing particles is 0.01-1.0 μm; and/or the coating thickness of the porous coating layer is 5 nm-500 nm.
6. The composite positive electrode material according to claim 5, wherein the material of the positive electrode active particles comprises LiCoO 2 、Li(Ni x1 Co x2 Mn x3 )O 2 、LiMn 2 O 4 、LiFePO 4 、LiMnPO 4 、LiMn i Fe 1-i PO 4 、Li 3 V 2 (PO4) 3 Wherein 0 < x1 < 1,0 < x2 < 1,0 < x3 < 1, and x1+x2+x3=1, 0 < i < 1;
and/or the lithium supplementing particles comprise a compound with a chemical formula of Li x M y O z Wherein 1 is<x<8，0.1<y<3，0<z<8, M comprises at least one transition metal element of iron, cobalt, zirconium, nickel and manganese;
and/or the material of the reducing particles comprises at least one of magnesium, zinc, lead, copper, tin, ferrous sulfide, molybdenum sulfide, tin sulfide, argon copper sulfide, tungsten sulfide and cobalt sulfide;
and/or the carbon material comprises at least one of amorphous carbon, carbon fiber, graphite, graphene.
7. The preparation method of the composite positive electrode material is characterized by comprising the following steps of:
preparing positive electrode active particles;
and preparing lithium supplementing particles loaded in a dot form on the surface of the positive electrode active material to obtain the composite positive electrode material.
8. The method of preparing a composite positive electrode material according to claim 7, wherein the step of preparing positive electrode active particles comprises: raw material components are obtained according to the stoichiometric ratio of each element in the positive electrode active material, and are mixed and sintered in inert atmosphere to prepare the positive electrode active particles;
And/or the step of loading the lithium supplementing particles on the surface of the positive electrode active material comprises the following steps:
preparing a porous coating layer on the surface of the positive electrode active particles to obtain coated particles;
and preparing lithium supplementing particles in the pores of the porous coating layer to obtain the composite anode material.
9. The method of preparing a composite positive electrode material according to claim 8, wherein the step of preparing the porous coating layer comprises: mixing a pore-forming agent, an organic carbon source and the positive electrode active particles, and then performing first sintering treatment under inert atmosphere to form the porous coating layer on the surfaces of the positive electrode active particles;
and/or, the preparation steps of the lithium supplementing particles comprise: mixing a lithium source, a transition metal source and the coated particles, and then performing second sintering treatment in an inert atmosphere to form a lithium supplementing material which is deposited in the pores of the porous coating layer to form the lithium supplementing particles;
and/or, further comprising the step of preparing reducing particles on the surface of the lithium supplementing particles and the surface of the porous coating layer: and carrying out vacuum evaporation deposition on the reducing metal and/or metal sulfide before and/or after the formation of the lithium supplementing particles, and loading the reducing particles on the surfaces of the lithium supplementing particles and the surface of the porous coating layer.
10. The method for producing a composite positive electrode material according to claim 9, wherein the mass ratio of the pore-forming agent, the organic carbon source, and the positive electrode active particles is (1 to 5): (5-25)%: (70-94)%;
and/or the mass ratio of the lithium source, the transition metal source and the coated particles is (0.08-1.55)%: (0.52-10.35)%: (88.10-99.40)%;
and/or the mass ratio of the total amount of the reducing metal and the metal sulfide to the particles to be supported is (0.3 to 6.6)%: (93.4-99.7)%;
and/or, the conditions of the first sintering process include: heating to 600-700 ℃ at a speed of 2-5 ℃ per minute under the condition that the flow rate of inert atmosphere is 300-1000 ml/min, and preserving heat for 1-10 h;
and/or, the conditions of the second sintering treatment include: heating to 700-1000 ℃ at a speed of 1-10 ℃/min under the condition that the flow rate of inert atmosphere is 5-200 ml/min, and then preserving heat for 0.5-1 h;
and/or, the conditions of the vacuum evaporation deposition comprise: vacuum degree of evaporation chamber is 10 -2 ～10 -6 Pa, the distance between the target and the base material is 1.0 cm-20 cm, the evaporation is regulated to 1-5 gears by a pressure regulator, the current is 10A-40A, and the residence time is 10S-60S.
11. The method for preparing a composite positive electrode material according to claim 9 or 10, wherein the material of the positive electrode active particles comprises LiCoO 2 、Li(Ni x1 Co x2 Mn x3 )O 2 、LiMn 2 O 4 、LiFePO 4 、LiMnPO 4 、LiMn i Fe 1-i PO 4 、Li 3 V 2 (PO4) 3 Wherein 0 < x1 < 1,0 < x2 < 1,0 < x3 < 1, and x1+x2+x3=1, 0 < i < 1;
and/or the pore-forming agent comprises at least one of glycerol, urea, melamine and dicyandiamide;
and/or the organic carbon source comprises at least one of asphalt, resin, oleylamine, oleic acid, cellulose, and glucose;
and/or the lithium source comprises LiOH, li 2 CO 3 、Li 2 O、Li 2 C 2 O 4 At least one of (a) and (b);
and/or the transition metal source comprises an oxide and/or hydroxide of at least one transition metal element of iron, cobalt, zirconium, nickel, manganese;
and/or the pore size of the pores in the porous coating layer is 0.1-1.0 μm.
12. A secondary battery, wherein the positive plate of the secondary battery comprises the composite positive electrode material according to any one of claims 1 to 6 or the composite positive electrode material prepared by the method according to any one of claims 7 to 11.
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