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CN118431399A - Secondary battery and electronic device - Google Patents

Secondary battery and electronic device Download PDF

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Publication number
CN118431399A
CN118431399A CN202410508755.6A CN202410508755A CN118431399A CN 118431399 A CN118431399 A CN 118431399A CN 202410508755 A CN202410508755 A CN 202410508755A CN 118431399 A CN118431399 A CN 118431399A
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positive electrode
ltoreq
nickel
secondary battery
manganese
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Inventor
盘如萍
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Xiamen Xinneng'an Technology Co ltd
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Xiamen Xinneng'an Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Nanotechnology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The application provides a secondary battery and an electronic device, wherein the secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel cobalt manganese ternary material and lithium iron manganese phosphate, the particle size Dv50 of the nickel cobalt manganese ternary material is D1 mu m, the particle size Dv50 of the lithium iron manganese phosphate is D2 mu m, the particle size Dv90 of the nickel cobalt manganese ternary material is D3 mu m, the particle size Dv90 of the lithium iron manganese phosphate is D4 mu m, D1 is more than or equal to 5.6,0.5 and less than or equal to 4, D3 is more than or equal to 5 and less than or equal to 18, and D4 is more than or equal to 10 and less than or equal to 30; the conductive agent comprises single-walled carbon nanotubes, the length of the single-walled carbon nanotubes is L nm, the diameter of the single-walled carbon nanotubes is D nm, the length-diameter ratio of the single-walled carbon nanotubes is X, X=L/D, X is more than or equal to 1667 and less than or equal to 40000, and L is more than or equal to 10000 and less than or equal to 40000. The particle diameters Dv50 and Dv90 of the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate, as well as the length-diameter ratio and the length of the single-wall carbon nano tube are regulated and controlled within the range of the application, thereby being beneficial to improving the capacity and the cycle performance of the secondary battery.

Description

Secondary battery and electronic device
Technical Field
The present application relates to the field of electrochemical technology, and in particular, to a secondary battery and an electronic device.
Background
The positive active material of the lithium ion battery comprises nickel cobalt manganese ternary material (NCM), lithium iron manganese phosphate (LFMP) and the like. The NCM with high energy density and the LFMP with high safety are mixed together to be used as the positive electrode active material, so that the advantages of the NCM and the LFMP can be simultaneously exerted, the comprehensive performance of the positive electrode active material is improved, and the lithium ion battery has higher energy density, and also has better safety performance and cycle performance.
However, the two positive electrode active materials are directly mixed, and the large difference of the particle sizes of the two positive electrode active materials can lead to less distribution of the conductive agent on the surface of the NCM, so that partial capacity of the NCM is difficult to develop, and the capacity and the cycle performance of the lithium ion battery are affected. At present, a method for increasing the content of the conductive agent is generally adopted to solve the problem that the distribution of the conductive agent on the NCM surface is less, but increasing the content of the conductive agent reduces the energy density of the lithium ion battery and increases the cost.
Disclosure of Invention
The application aims to provide a secondary battery and an electronic device, so as to improve the capacity and cycle performance of the secondary battery. The specific technical scheme is as follows:
The first aspect of the application provides a secondary battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel-cobalt-manganese ternary material and a ferric manganese lithium phosphate, the particle size Dv50 of the nickel-cobalt-manganese ternary material is D1 mu m, the particle size Dv50 of the ferric manganese lithium phosphate is D2 mu m, the particle size Dv90 of the nickel-cobalt-manganese ternary material is D3 mu m, the particle size Dv90 of the ferric manganese lithium phosphate is D4 mu m, D1 is not less than or equal to 5.6,0.5 is not more than 4, D3 is not more than 18, and D4 is not more than 10 and not more than 30; the conductive agent comprises single-walled carbon nanotubes, the length of the single-walled carbon nanotubes is L nm, the diameter of the single-walled carbon nanotubes is D nm, the length-diameter ratio of the single-walled carbon nanotubes is X, X=L/D, X is 1667-40000, and optionally, X is 6667-40000; 10000.ltoreq.L.ltoreq.40000, alternatively 20000.ltoreq.L.ltoreq.40000. The positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel cobalt manganese ternary material and a ferric manganese lithium phosphate, the particle sizes Dv50 and Dv90 of the nickel cobalt manganese ternary material, the particle sizes Dv50 and Dv90 of the ferric manganese lithium phosphate, the conductive agent comprises a single-wall carbon nano tube and the length-diameter ratio of the single-wall carbon nano tube, the length is within the range of the application, the nickel cobalt manganese ternary material and the ferric manganese lithium phosphate have proper particle sizes and particle size distribution, the single-wall carbon nano tube has proper length-diameter ratio and length, the single-wall carbon nano tube has higher conductivity, higher strength and better flexibility, a conductive network of a blending system can be perfected under the condition of lower addition amount, more durable connection is formed between the positive electrode active materials, and the ion transmission of the blending system is effectively improved, so that the capacity and the cycle performance of a secondary battery are facilitated to be improved.
In one or more embodiments of the application, 1.ltoreq.D.ltoreq.6, alternatively 1.ltoreq.D.ltoreq.3. By regulating the value of D within the range of the application, the single-walled carbon nanotube has proper diameter, relatively fewer defects and relatively higher conductivity, is beneficial to electron conduction and further improves the capacity and the cycle performance of the secondary battery.
In one or more embodiments of the application, 1.5.ltoreq.D3/D1.ltoreq.3.5, 3.ltoreq.D4/D2.ltoreq.25. By regulating the values of D3/D1 and D4/D2 within the range of the application, the uniformity of the nickel-cobalt-manganese ternary material particles and the ferric manganese lithium phosphate particles is better, and the conductive agent is more uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the ferric manganese lithium phosphate particles, so that the conductive network in the blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In one or more embodiments of the application, the particle size Dv10 of the nickel-cobalt-manganese ternary material is D5 μm, and the particle size Dv10 of the lithium iron-manganese phosphate is D6 μm, D5 is 1.8.ltoreq.D5.ltoreq. 2.8,0.2.ltoreq.D6.ltoreq.0.5. By regulating and controlling the particle size Dv10 of the nickel-cobalt-manganese ternary material and the particle size Dv10 of the lithium iron manganese phosphate within the range of the application, the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate have proper particle size distribution, and the conductive agent is more uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the lithium iron manganese phosphate particles, so that a conductive network in a blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In one or more embodiments of the present application, the conductive agent is present in an amount of 0.2% to 0.8% by mass based on the mass of the positive electrode material layer. The conductive agent has proper mass percentage content by regulating and controlling the mass percentage content W1 of the conductive agent within the range of the application, can be effectively connected with the positive electrode active material, can form a more perfect conductive network in a blending system, and is beneficial to further improving the capacity and the cycle performance of the secondary battery.
In one or more embodiments of the present application, the nickel cobalt manganese ternary material has a mass percentage Wa of 35% to 95% and the iron manganese lithium phosphate has a mass percentage Wb of 5% to 65%, based on the mass of the nickel cobalt manganese ternary material and the iron manganese lithium phosphate. The particle size of the nickel-cobalt-manganese ternary material is different from that of the lithium iron manganese phosphate, and the particle size difference of the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate in a blending system can be reduced to a certain extent by regulating and controlling the mass percentage content Wa of the nickel-cobalt-manganese ternary material and the mass percentage content Wb of the lithium iron manganese phosphate in the range of the application, so that the conductive agent is uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the lithium iron manganese phosphate particles, the conductive network in the blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In one or more embodiments of the present application, the positive electrode material layer further includes a binder, the mass percentage W2 of the positive electrode active material is 96.8% to 98.8%, and the mass percentage W3 of the binder is 1% to 2.4%, based on the mass of the positive electrode material layer. By regulating the mass percentage content W2 of the positive electrode active material and the mass percentage content W3 of the binder within the scope of the application, the positive electrode active material, the binder and the conductive agent all have proper mass percentage content, and the secondary battery has higher capacity, better cycle performance and lower internal resistance.
A second aspect of the present application provides an electronic device comprising the secondary battery in any one of the foregoing embodiments. Therefore, the electronic device provided by the application has good service performance.
The application has the beneficial effects that:
The application provides a secondary battery and an electronic device, wherein the secondary battery comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel cobalt manganese ternary material and a manganese iron phosphate lithium, the particle size Dv50 of the nickel cobalt manganese ternary material is D1 mu m, the particle size Dv50 of the manganese iron phosphate lithium is D2 mu m, the particle size Dv90 of the nickel cobalt manganese ternary material is D3 mu m, the particle size Dv90 of the manganese iron phosphate lithium is D4 mu m, D1 is not less than or equal to 5.6,0.5 is not more than 4, D3 is not more than 18, and D4 is not less than 10 and not more than 30; the conductive agent comprises single-walled carbon nanotubes, the length of the single-walled carbon nanotubes is L nm, the diameter of the single-walled carbon nanotubes is D nm, the length-diameter ratio of the single-walled carbon nanotubes is X, X=L/D, X is more than or equal to 1667 and less than or equal to 40000, and L is more than or equal to 10000 and less than or equal to 40000. The positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel cobalt manganese ternary material, lithium iron manganese phosphate and nickel cobalt manganese ternary material, the particle sizes Dv50 and Dv90 of the lithium iron manganese phosphate, and the conductive agent comprises a single-walled carbon nanotube and the length-diameter ratio and the length of the single-walled carbon nanotube are controlled within the range of the application, so that the capacity and the cycle performance of the secondary battery are improved.
Of course, it is not necessary for any one product or method of practicing the application to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the application, and other embodiments may be obtained according to these drawings to those skilled in the art.
FIG. 1 is a Scanning Electron Microscope (SEM) image of a positive electrode sheet of comparative examples 1-2 of the present application;
FIG. 2 is a Scanning Electron Microscope (SEM) image of the positive electrode sheet of example 1-1 of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments obtained by the person skilled in the art based on the present application fall within the scope of protection of the present application.
In the following, the present application will be explained with reference to a lithium ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium ion battery. The specific technical scheme is as follows:
The application provides a secondary battery, which comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel cobalt manganese ternary material and lithium iron phosphate, the particle size Dv50 of the nickel cobalt manganese ternary material is D1 mu m, the particle size Dv50 of the lithium iron phosphate is D2 mu m, the particle size Dv90 of the nickel cobalt manganese ternary material is D3 mu m, the particle size Dv90 of the lithium iron phosphate is D4 mu m, and D1 is less than or equal to 3 and less than or equal to 5.6, and illustratively, D1 can be 3, 3.2, 3.4, 3.6, 3.8, 4, 4.6, 4.8, 5, 5.2, 5.4, 5.6 or a range formed by any two of the values. D2.ltoreq.4.0.5.ltoreq.d2.ltoreq.4, illustratively, D2 may be 0.5, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4 or a range of any two values from the above. D3.ltoreq.18, and D3 may be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or a range of any two of the above values. 10.ltoreq.D4.ltoreq.30, D4 may be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 or a range of any two values as mentioned above, for example.
The conductive agent includes a single-walled carbon nanotube having a length of L nm, a diameter of D nm, an aspect ratio of X, X=L/D, 1667.ltoreq.X.ltoreq.40000, optionally 6667.ltoreq.X.ltoreq.40000, and X may be 1667, 2000, 3000, 4000, 5000, 6000, 6667, 7000, 8000, 9000, 10000, 15000, 20000, 25000, 30000, 35000, 40000, or a range of any two of the above values, for example. 10000.ltoreq.L.ltoreq.40000, alternatively 20000.ltoreq.L.ltoreq.40000, L may be 10000, 12000, 14000, 16000, 18000, 20000, 22000, 24000, 26000, 28000, 30000, 32000, 34000, 36000, 38000, 40000 or a range consisting of any two of the above values, for example. In the present application, the nickel cobalt manganese ternary material includes at least one of LiNi0.8Co0.1Mn0.1O2(NCM811)、LiNi0.6Co0.2Mn0.2O2(NCM622)、LiNi0.5Co0.2Mn0.3O2(NCM523) or LiNi 1/3Co1/3Mn1/3O2 (NCM 111); the chemical formula of the lithium iron manganese phosphate is LiMn nFe1-nPO4, and n is more than 0.5 and less than 0.9. Illustratively, the value of n may be 0.52, 0.54, 0.56, 0.58, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.89, or a range of any two of the values recited above. The above-mentioned "positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer may be disposed on one surface of the positive electrode current collector in the thickness direction thereof, or may be disposed on both surfaces of the positive electrode current collector in the thickness direction thereof. The "surface" here may be the entire region of the positive electrode current collector or may be a partial region of the positive electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved.
In the present application, dv50 means a particle diameter of 50% in volume as measured from a small particle diameter in a particle size distribution based on the volume of the material; dv90 is the particle size which reaches 90% by volume as measured from the small particle size in the particle size distribution based on the volume of the material.
The inventor researches find that in general, the particle sizes of the nickel-cobalt-manganese ternary material and the lithium iron-manganese phosphate are generally greatly different, so that the specific surface area of the lithium iron-manganese phosphate is far larger than that of the nickel-cobalt-manganese ternary material. The two materials with overlarge particle size difference are blended, the conductive agent is unevenly distributed, the nickel-cobalt-manganese ternary material is easy to form an island, as shown in fig. 1, the particles with larger particle size are nickel-cobalt-manganese ternary material, the particles with smaller particle size are ferric manganese lithium phosphate, the conductive agent on the surfaces of the particles of the nickel-cobalt-manganese ternary material with larger particle size is less in distribution, which indicates that the blending can lead to less conductive agent on the surfaces of the nickel-cobalt-manganese ternary material with smaller specific surface area, and the capacity of the secondary battery cannot be normally exerted. At present, a method for increasing the content of the conductive agent is generally adopted to solve the problem that the distribution of the conductive agent on the surface of the nickel-cobalt-manganese ternary material is less, but increasing the content of the conductive agent can reduce the energy density of the lithium ion battery and increase the cost. By adding single-wall carbon nanotubes (SWCNTs) into a blending system of nickel cobalt manganese ternary materials and lithium iron manganese phosphate, as shown in figure 2, spherical particles with larger particle sizes are nickel cobalt manganese ternary materials, particles with smaller particle sizes are lithium iron manganese phosphate, linear substances are single-wall carbon nanotubes, the single-wall carbon nanotubes are distributed on the surfaces of the two materials and between the two materials, the nickel cobalt manganese ternary materials and the lithium iron manganese phosphate are better connected, the conductive network of the blending system can be perfected, thereby effectively improving the ion transmission of the blending system, ensuring that the capacities of the two materials in the blending system can be fully exerted, simultaneously ensuring that the secondary battery has more excellent cycle performance, and also to reduce the cost of the secondary battery. When the particle diameters Dv50 and Dv90 of the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate are too small, the processing performance of the positive electrode plate is poor, the compaction density of the positive electrode material layer is reduced, and therefore the energy density of the secondary battery is reduced; when the particle diameters Dv50, dv90 of the nickel-cobalt-manganese ternary material and the lithium iron-manganese phosphate are excessively large, the dynamic performance of the secondary battery may be poor, the discharge capacity of the secondary battery may be reduced, and the cycle performance of the secondary battery may be deteriorated. When the length-diameter ratio X of the single-walled carbon nanotube is too large, for example, greater than 40000, the length of the single-walled carbon nanotube is too large, the manufacturing process of the single-walled carbon nanotube is complex, and the actual use of the single-walled carbon nanotube is affected; when the length-diameter ratio X of the single-walled carbon nanotubes is too small, for example smaller than 1667, the length of the single-walled carbon nanotubes is too small, and the conductive network of the blending system cannot be effectively improved; the excessive diameter of the single-walled carbon nanotubes can cause the defect number of the single-walled carbon nanotubes to increase, reduce the conductivity of the single-walled carbon nanotubes, and affect the capacity and cycle performance of the secondary battery. the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises nickel cobalt manganese ternary material and ferric manganese lithium phosphate, the particle sizes Dv50 and Dv90 of the nickel cobalt manganese ternary material, the particle sizes Dv50 and Dv90 of the ferric manganese lithium phosphate, the conductive agent comprises single-wall carbon nano tubes and the length-diameter ratio of the single-wall carbon nano tubes, the length is within the range of the application, the nickel cobalt manganese ternary material and the ferric manganese lithium phosphate have proper particle sizes and particle size distribution, the single-wall carbon nano tubes have proper length-diameter ratio and length, the single-wall carbon nano tubes have higher conductivity, higher strength and better flexibility, and the conductive network of a blending system can be perfected under the condition of lower addition, and a relatively durable connection is formed between the positive electrode active materials, so that the ion transmission of a blending system is effectively improved, and the capacity and the cycle performance of the secondary battery are improved.
In one embodiment of the application, 1.ltoreq.D.ltoreq.6, alternatively 1.ltoreq.D.ltoreq.3, and D may be 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6 or a range consisting of any two of the values mentioned above, for example. By regulating the value of D within the range of the application, the single-walled carbon nanotube has proper diameter, relatively fewer defects and relatively higher conductivity, is beneficial to electron conduction and further improves the capacity and the cycle performance of the secondary battery.
In one embodiment of the application, 1.5.ltoreq.D3/D1.ltoreq.3.5, illustratively, D3/D1 may be 1.5, 1.7, 1.9, 2, 2.1, 2.3, 2.5, 2.7, 2.9, 3, 3.1, 3.3, 3.5 or a range of any two values mentioned above; 3.ltoreq.D4/D2.ltoreq.25, the D4/D2 may be 3、3.3、3.5、3.7、4、4.3、4.5、4.7、5、5.3、5.5、5.7、6、6.3、6.5、6.7、7、7.3、7.5、7.7、8、9、10、11、12、13、14、15、16、17、18、19、20、21、22、23、24、25 or a range of any two values as described above, for example. By regulating the values of D3/D1 and D4/D2 within the range of the application, the uniformity of the nickel-cobalt-manganese ternary material particles and the ferric manganese lithium phosphate particles is better, and the conductive agent is more uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the ferric manganese lithium phosphate particles, so that the conductive network in the blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In one embodiment of the application, the particle size Dv10 of the nickel cobalt manganese ternary material is D5 μm, the particle size Dv10 of the lithium iron manganese phosphate is D6 μm, 1.8.ltoreq.d5.ltoreq.2.8, and illustratively, D5 may be 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or a range consisting of any two of the foregoing values; 0.2.ltoreq.D6.ltoreq.0.5, illustratively, D6 may be 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5 or ranges of any two of the values recited above. By regulating and controlling the particle size Dv10 of the nickel-cobalt-manganese ternary material and the particle size Dv10 of the lithium iron manganese phosphate within the range of the application, the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate have proper particle size distribution, and the conductive agent is more uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the lithium iron manganese phosphate particles, so that a conductive network in a blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In the present application, dv10 means a particle size which reaches 10% by volume as measured from a small particle size in a particle size distribution based on the volume of the material.
In one embodiment of the present application, the mass percentage W1 of the conductive agent is 0.2% to 0.8% based on the mass of the positive electrode material layer, and illustratively, the mass percentage W1 of the conductive agent may be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or a range of any two of the above numerical values. The conductive agent has proper mass percentage content by regulating and controlling the mass percentage content W1 of the conductive agent within the range of the application, can be effectively connected with the positive electrode active material, can form a more perfect conductive network in a blending system, and is beneficial to further improving the capacity and the cycle performance of the secondary battery.
In one embodiment of the present application, the weight percentage Wa of the nickel cobalt manganese ternary material is 35% to 95% based on the weight of the nickel cobalt manganese ternary material and the lithium iron manganese phosphate, and illustratively, the weight percentage Wa of the nickel cobalt manganese ternary material may be 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or a range of any two of the above numerical values. The mass percentage Wb of the lithium iron manganese phosphate is 5% to 65%, and illustratively, the mass percentage Wb of the lithium iron manganese phosphate may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or a range of any two of the above numerical values. The particle size of the nickel-cobalt-manganese ternary material is different from that of the lithium iron manganese phosphate, and the particle size difference of the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate in a blending system can be reduced to a certain extent by regulating and controlling the mass percentage content Wa of the nickel-cobalt-manganese ternary material and the mass percentage content Wb of the lithium iron manganese phosphate in the range of the application, so that the conductive agent is uniformly distributed on the surfaces of the nickel-cobalt-manganese ternary material particles and the lithium iron manganese phosphate particles, the conductive network in the blending system is more perfect, and the capacity and the cycle performance of the secondary battery are further improved.
In one embodiment of the present application, the positive electrode material layer further includes a binder including at least one of polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, polystyrene butadiene copolymer (styrene butadiene rubber), sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hydroxymethyl cellulose, or potassium hydroxymethyl cellulose. The mass percentage W2 of the positive electrode active material is 96.8% to 98.8% based on the mass of the positive electrode material layer, and illustratively, the mass percentage W2 of the positive electrode active material may be 96.8%, 97%, 97.2%, 97.4%, 97.6%, 97.8%, 98%, 98.2%, 98.4%, 98.6%, 98.8% or a range composed of any two of the above values. The mass percentage of the binder W3 is 1% to 2.4%, and illustratively, the mass percentage of the binder W3 may be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, or a range of any two of the above numerical values. By regulating the mass percentage content W2 of the positive electrode active material and the mass percentage content W3 of the binder within the scope of the application, the positive electrode active material, the binder and the conductive agent all have proper mass percentage content, and the secondary battery has higher capacity, better cycle performance and lower internal resistance.
The method for regulating and controlling the particle sizes Dv10, dv50 and Dv90 of the nickel-cobalt-manganese ternary material is not particularly limited, so long as the purpose of the application can be achieved. Illustratively, the particle sizes Dv10, dv50, dv90 of the nickel-cobalt-manganese ternary material may be controlled by grinding the nickel-cobalt-manganese ternary material. For example, the particle sizes Dv10, dv50 and Dv90 of the nickel-cobalt-manganese ternary material can be regulated by regulating the grinding time. Illustratively, when other conditions are unchanged, the grinding time is prolonged, the particle size Dv10 of the nickel-cobalt-manganese ternary material is reduced, the particle size Dv50 of the nickel-cobalt-manganese ternary material is reduced, and the particle size Dv90 of the nickel-cobalt-manganese ternary material is reduced; the grinding time is shortened, the particle size Dv10 of the nickel-cobalt-manganese ternary material is increased, the particle size Dv50 of the nickel-cobalt-manganese ternary material is increased, and the particle size Dv90 of the nickel-cobalt-manganese ternary material is increased.
The method of controlling the particle diameters Dv10, dv50, dv90 of lithium iron manganese phosphate according to the present application is not particularly limited as long as the object of the present application can be achieved. For example, the particle sizes Dv10, dv50, dv90 of lithium iron manganese phosphate can be controlled by grinding the lithium iron manganese phosphate. For example, the particle diameters Dv10, dv50, dv90 of lithium iron manganese phosphate can be controlled by controlling the grinding time. Illustratively, when other conditions are unchanged, the grinding time is prolonged, the particle size Dv10 of the lithium iron manganese phosphate is reduced, the particle size Dv50 of the lithium iron manganese phosphate is reduced, and the particle size Dv90 of the lithium iron manganese phosphate is reduced; the grinding time is shortened, the particle diameter Dv10 of the lithium iron manganese phosphate is increased, the particle diameter Dv50 of the lithium iron manganese phosphate is increased, and the particle diameter Dv90 of the lithium iron manganese phosphate is increased.
The method of controlling the value of D3/D1 is not particularly limited as long as the object of the present application can be achieved. Illustratively, the value of D3/D1 may be regulated by regulating the respective values of D3 and D1, the regulation methods of D3, D1 being as described above.
The method of controlling the value of D4/D2 is not particularly limited as long as the object of the present application can be achieved. Illustratively, the value of D4/D2 may be regulated by regulating the respective values of D4 and D2, the regulation methods of D4, D2 being as described above.
The materials with different particle sizes can be obtained through purchase, and the particle sizes of the materials are tested by combining the particle size test method provided by the application, and the materials with the required particle sizes are selected.
Materials of different aspect ratios, lengths, diameters in the present application can be obtained by purchase, and the present application is not particularly limited as long as the object of the present application can be achieved.
The positive electrode current collector of the present application is not particularly limited as long as the object of the present application can be achieved, and for example, aluminum foil, aluminum alloy foil, or a composite current collector (for example, an aluminum-carbon composite current collector) may be included.
The thickness of the positive electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, the positive electrode current collector has a thickness of 5 μm to 20 μm. The thickness of the positive electrode material layer is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the single-sided positive electrode material layer is 30 μm to 250 μm. The thickness of the positive electrode sheet is not particularly limited as long as the object of the present application can be achieved, for example, the positive electrode sheet has a thickness of 50 μm to 500 μm.
Optionally, the positive electrode sheet may further comprise a conductive layer located between the positive electrode current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited in the present application, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and may be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application, and may be selected according to actual needs by those skilled in the art as long as the object of the present application can be achieved.
In the present application, the secondary battery further includes a negative electrode tab. The negative electrode tab includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The above-mentioned "anode material layer provided on at least one surface of the anode current collector" means that the anode material layer may be provided on one surface of the anode current collector in the thickness direction thereof, or may be provided on both surfaces of the anode current collector in the thickness direction thereof. The "surface" here may be the entire region of the negative electrode current collector or may be a partial region of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved. The negative electrode current collector of the present application is not particularly limited as long as the object of the present application can be achieved, and for example, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper, or composite current collector may be included.
The anode material layer of the present application includes an anode active material. The anode active material of the present application is not particularly limited as long as the object of the present application can be achieved, and for example, the anode active material may include at least one of natural graphite, artificial graphite, mesophase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite, siO x (0.5 < x < 1.6), li-Sn alloy, li-Sn-O alloy, sn, snO, snO 2, spinel-structured lithium titanate Li 4Ti5O12, li-Al alloy, or metallic lithium. The negative electrode material layer of the present application further includes a negative electrode binder and a negative electrode conductive agent. The anode binder and the anode conductive agent in the anode material layer of the present application are not particularly limited as long as the object of the present application can be achieved, and for example, the anode binder may be at least one of the above binders. The negative electrode conductive agent comprises at least one of conductive carbon black, carbon nanotubes, carbon fibers, crystalline flake graphite, graphene, a metal material or a conductive polymer. The conductive carbon black includes at least one of Super P, acetylene black or ketjen black. The carbon nanotubes include single-walled carbon nanotubes and/or multi-walled carbon nanotubes (MWCNTs). The carbon fibers include Vapor Grown Carbon Fibers (VGCF) and/or nano carbon fibers. The metal material includes metal powder and/or metal fiber, and specifically, the metal includes at least one of copper, nickel, aluminum or silver. The conductive polymer includes at least one of a polyphenylene derivative, polyaniline, polythiophene, polyacetylene, or polypyrrole. The mass ratio of the anode active material, the anode binder and the anode conductive agent in the anode material layer is not particularly limited, and can be selected by a person skilled in the art according to actual needs as long as the purpose of the present application can be achieved.
The thickness of the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode current collector is 4 μm to 12 μm. The thickness of the anode material layer is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the single-sided anode material layer is 30 μm to 250 μm. The thickness of the negative electrode tab is not particularly limited as long as the object of the present application can be achieved, for example, the thickness of the negative electrode tab is 30 μm to 500 μm.
Optionally, the negative electrode tab may further comprise a conductive layer located between the negative electrode current collector and the negative electrode material layer. The composition of the conductive layer is not particularly limited in the present application, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application, and may be at least one of the above-mentioned conductive agent and the above-mentioned binder. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application, and may be selected according to actual needs by those skilled in the art as long as the object of the present application can be achieved.
In the present application, the secondary battery further includes an electrolyte. The electrolyte includes a lithium salt and a nonaqueous solvent. The lithium salt may include various lithium salts commonly used in the art, such as at least one of LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、Li2SiF6、 lithium bis (oxalato) borate (LiBOB) or lithium difluoroborate. The nonaqueous solvent is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The carbonate compound may include, but is not limited to, at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorocarbonate compound. The chain carbonate compound may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl Propyl Carbonate (MPC), ethylene Propyl Carbonate (EPC), or ethylmethyl carbonate (EMC). The above-mentioned cyclic carbonate compound may include, but is not limited to, at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC) or Vinyl Ethylene Carbonate (VEC). The above-mentioned fluorocarbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. The above carboxylic acid ester compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, or caprolactone. The ether compound may include, but is not limited to, at least one of dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application is not particularly limited as long as the object of the present application can be achieved, as long as the mass percentage of the lithium salt and the nonaqueous solvent is not particularly limited.
In the present application, the secondary battery further includes a separator. The diaphragm is used for separating the positive pole piece from the negative pole piece, prevents internal short circuit of the secondary battery, allows electrolyte ions to pass through freely, and does not influence the electrochemical charge and discharge process. The separator is not particularly limited as long as the object of the present application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of Polyethylene (PE), polypropylene (PP) -based Polyolefin (PO), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid; the type of separator may include at least one of a woven film, a nonwoven film, a microporous film, a composite film, a rolled film, or a spun film.
In the present application, the separator may include a base film and a surface treatment layer. The base film may be a nonwoven fabric or a composite film having a porous structure, and the material of the base film may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, at least one surface of the base film is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder for separator, and the present application is not particularly limited, and the inorganic particles may include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, for example. The binder for a separator according to the present application is not particularly limited, and may be at least one of the above binders, for example. The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). The thickness of the base film is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the base film may be 7 μm to 14 μm. The thickness of the inorganic layer is not particularly limited as long as the object of the present application can be achieved. For example, the inorganic layer may have a thickness of 2 μm to 4 μm. The coating weight of the polymer layer is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the coating weight of the polymer layer may be 1mg/1540.25mm 2 to 2mg/1540.25mm 2.
The secondary battery of the present application further includes a pouch for accommodating the positive electrode tab, the separator, the negative electrode tab, and the electrolyte, and other components known in the art in the secondary battery, and the present application is not limited thereto. The present application is not particularly limited, and may be any known in the art as long as the object of the present application can be achieved.
In the present application, the secondary battery may include, but is not limited to: lithium metal secondary batteries, lithium ion secondary batteries (lithium ion batteries), lithium polymer secondary batteries, lithium ion polymer secondary batteries, and the like.
The process of preparing the secondary battery of the present application is well known to those skilled in the art, and the present application is not particularly limited, and may include, for example, but not limited to, the following steps: sequentially stacking the positive electrode plate, the diaphragm and the negative electrode plate, winding and folding the positive electrode plate, the diaphragm and the negative electrode plate according to the need to obtain an electrode assembly with a winding structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain a secondary battery; or sequentially stacking the positive electrode plate, the diaphragm and the negative electrode plate, fixing four corners of the whole lamination structure by using an adhesive tape to obtain an electrode assembly of the lamination structure, placing the electrode assembly into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain the secondary battery. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the package bag as needed, thereby preventing the pressure inside the secondary battery from rising and overcharging and discharging. Wherein the package is a package known in the art, and the application is not limited thereto.
A second aspect of the present application provides an electronic device comprising the secondary battery in any one of the foregoing embodiments. Therefore, the electronic device provided by the application has good service performance.
The kind of the electronic device is not particularly limited in the present application, and it may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash light, a camera, a household large-sized battery, a lithium ion capacitor, and the like.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. The various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "parts" and "%" are mass references.
Test method and apparatus:
particle size testing:
The particle size of the nickel cobalt manganese ternary material was measured using a malvern particle size tester (model MasterSizer 2000). Adding 0.02g of the nickel-cobalt-manganese ternary material into a 50mL clean beaker, adding 20mL of dispersing agent ethanol, and performing ultrasonic treatment in a 120W ultrasonic cleaner for 30min to completely disperse the nickel-cobalt-manganese ternary material in the ethanol to obtain a sample dispersion. And testing the sample dispersion liquid by using a Markov particle size tester to obtain particle sizes Dv10, dv50 and Dv90 of the nickel-cobalt-manganese ternary material.
The particle size of the lithium iron manganese phosphate was measured using a malvern particle size tester (model MasterSizer 2000). 0.02g of lithium iron manganese phosphate is added into a 50mL clean beaker, 20mL of dispersant ethanol is added, and ultrasonic treatment is carried out for 30min in a 120W ultrasonic cleaner, so that the lithium iron manganese phosphate is completely dispersed in the ethanol, and a sample dispersion liquid is obtained. The sample dispersion liquid was tested by using a malvern particle size tester to obtain particle sizes Dv10, dv50, dv90 of lithium iron manganese phosphate.
Aspect ratio test of single-walled carbon nanotubes:
Discharging the lithium ion battery to 2.8V and disassembling to obtain the positive electrode plate. 0.02g of the positive electrode material layer powder was scraped with a knife, dissolved with 100mL of N-methylpyrrolidone (NMP), centrifuged, and the supernatant was dropped on a conductive substrate and dried. The obtained sample is observed through a scanning electron microscope (model number is Helios 5 CX), the length L and the diameter D of the carbon nanotubes are obtained according to the track measurement of the carbon nanotubes, 100 carbon nanotubes are selected randomly for measurement, the length L and the diameter D of the single-wall carbon nanotubes are obtained by taking the average value, the length-diameter ratio X=L/D of the 100 single-wall carbon nanotubes is calculated, and the length-diameter ratio of the single-wall carbon nanotubes is obtained by taking the average value.
Capacity test:
And discharging the lithium ion battery to 2.8V at the constant current of 0.2C at the temperature of 25 ℃, standing for 5min, then charging to 4.3V at the constant current of 0.2C, charging to 0.02C at the constant voltage of 4.3V, standing for 5min, then discharging to 2.8V at the constant current of 0.2C, and recording that the discharge capacity at the moment is the capacity of the lithium ion battery.
And (3) testing the cycle performance:
At 25 ℃, the lithium ion battery is charged to 4.3V at a constant current of 0.2C, is charged to 0.02C at a constant voltage of 4.3V, is kept stand for 5min, and is then discharged to 2.8V at a constant current of 1C. The method is a charge-discharge cycle process, the first circle of discharge capacity is recorded as C 0, 1000 circles of charge-discharge cycles are performed in the mode, and the discharge capacity after the 1000 th circle of cycles is recorded as C 1000.
Capacity retention of 1000 cycles of lithium ion battery= (C 1000/C0) ×100%.
Example 1-1
< Preparation of Positive electrode sheet >
Mixing a nickel-cobalt-manganese ternary material (LiNi 0.8Co0.1Mn0.1O2) serving as an anode active material, lithium iron-manganese phosphate (LiMn 0.6Fe0.4PO4) serving as an anode active material, a single-walled carbon nanotube (SWCNT) and polyvinylidene fluoride (PVDF) according to a mass ratio of 78.4:19.6:0.5:1.5, adding N-methylpyrrolidone (NMP) serving as a solvent, preparing anode slurry with a solid content of 70wt%, and uniformly stirring by a vacuum stirrer to obtain the anode slurry. And uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 10 mu m, and drying at 90 ℃ to obtain a positive electrode plate with a single-sided coating positive electrode material layer, wherein the coating weight of the positive electrode material layer is 300g/m 2 during coating. And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating positive electrode material layer. Drying at 90 ℃, cold pressing, cutting, welding the tab and pasting the gummed paper to obtain the positive pole piece with the specification of 74mm multiplied by 867mm for standby. Wherein the compacted density of the positive electrode material layer after cold pressing is 3g/cm 3. The particle diameters Dv50 (i.e., D1), dv90 (i.e., D3), dv10 (i.e., D5), dv50 (i.e., D2), dv90 (i.e., D4), dv10 (i.e., D6), D3/D1, D4/D2 of the ternary nickel-cobalt-manganese material, and the ternary nickel-cobalt-manganese material were set as shown in table 1. The aspect ratio X, length L, and diameter D of the single-walled carbon nanotubes are shown in table 1. Based on the mass of the nickel-cobalt-manganese ternary material and the lithium iron manganese phosphate, the mass percentage Wa of the nickel-cobalt-manganese ternary material is 80%, and the mass percentage Wb of the lithium iron manganese phosphate is 20%.
< Preparation of negative electrode sheet >
Mixing negative active materials of artificial graphite, conductive carbon black (Super P) and Styrene Butadiene Rubber (SBR) according to a mass ratio of 96:1.5:2.5, adding deionized water as a solvent, and blending to obtain negative slurry with a solid content of 65wt%, and uniformly stirring by a vacuum stirrer to obtain the negative slurry. And uniformly coating the negative electrode slurry on one surface of a negative electrode current collector copper foil with the thickness of 10 mu m, and drying at the temperature of 110 ℃ to obtain a negative electrode plate with a single-side coated negative electrode material layer, wherein the coating weight of the negative electrode material layer is 140g/m 2 during coating. And repeating the steps on the other surface of the copper foil to obtain the negative electrode plate with the double-sided coating negative electrode material layer. Drying at 110deg.C, cold pressing, cutting, welding tab, and pasting adhesive paper to obtain 78mm×875mm negative electrode plate. Wherein the compacted density of the negative electrode material layer after cold pressing is 1.7g/cm 3.
< Preparation of electrolyte >
In an argon atmosphere glove box with the water content less than 10ppm, uniformly mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio EC:EMC: DEC=3:5:2 to obtain a base solvent, then adding lithium hexafluorophosphate (LiPF 6) serving as a lithium salt into the base solvent, and uniformly mixing to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass percentage of the lithium salt is 12.5 percent, and the balance is the basic solvent.
< Separator >
Polyethylene film with a thickness of 9 μm was selected as the separator.
< Preparation of lithium ion Battery >
Sequentially stacking the positive electrode plate, the diaphragm, the negative electrode plate and the diaphragm, enabling the diaphragm to be positioned between the positive electrode plate and the negative electrode plate to play a role in isolation, and then winding to obtain an electrode assembly; and placing the electrode assembly in an aluminum plastic film packaging bag, dehydrating at 80 ℃, injecting the prepared electrolyte, vacuum packaging, standing, forming (0.02C constant current charging to 3.3V, and then 0.1C constant current charging to 3.6V), and shaping to obtain the lithium ion battery.
Examples 1-2 to 1-19
The procedure of example 1-1 was repeated except that the milling time was adjusted so that the particle diameter Dv10 of the nickel-cobalt-manganese ternary material, the particle diameter Dv50 of the nickel-cobalt-manganese ternary material, the particle diameter Dv90 of the nickel-cobalt-manganese ternary material, the particle diameter Dv10 of the iron-manganese lithium phosphate, the particle diameter Dv50 of the iron-manganese lithium phosphate, and the particle diameter Dv90 of the iron-manganese lithium phosphate were as shown in table 1, and the relevant production parameters were adjusted in accordance with table 1.
Examples 2-1 to 2-10
The procedure of example 1-1 was repeated except that the relevant production parameters were adjusted in accordance with Table 2 in < production of positive electrode sheet >.
Comparative examples 1-1 to 1-4
The procedure of example 1-1 was repeated except that the relevant production parameters were adjusted in accordance with Table 1 in < production of positive electrode sheet >.
Comparative examples 1 to 5 to 1 to 9
The procedure of example 1-1 was repeated except that the milling time was adjusted so that the particle diameter Dv10 of the nickel-cobalt-manganese ternary material, the particle diameter Dv50 of the nickel-cobalt-manganese ternary material, the particle diameter Dv90 of the nickel-cobalt-manganese ternary material, the particle diameter Dv10 of the iron-manganese lithium phosphate, the particle diameter Dv50 of the iron-manganese lithium phosphate, and the particle diameter Dv90 of the iron-manganese lithium phosphate were as shown in table 1, and the relevant production parameters were adjusted in accordance with table 1.
Comparative examples 2-1 to 2-4
The procedure of example 1-1 was repeated except that the relevant production parameters were adjusted in accordance with Table 2 in < production of positive electrode sheet >.
The preparation parameters and the electrical properties of each example and comparative example are shown in tables 1 to 2.
TABLE 1
Note that: in table 1, "/" indicates no relevant preparation parameters.
Referring to table 1, as can be seen from examples 1-1 to 1-19 and comparative examples 1-1 to 1-9, by controlling the positive electrode material layer to include the positive electrode active material and the conductive agent, the positive electrode active material to include nickel cobalt manganese ternary material and iron manganese lithium phosphate, the particle diameters Dv50 and Dv90 of the nickel cobalt manganese ternary material, the particle diameters Dv50 and Dv90 of the iron manganese lithium phosphate, the conductive agent to include single-walled carbon nanotubes and the length-to-diameter ratio of the single-walled carbon nanotubes, and the length is within the scope of the present application, the capacity of the lithium ion battery is higher, the capacity retention rate of 1000 cycles is higher, and the lithium ion battery has higher capacity and better cycle performance. In comparative examples 1-1 to 1-9, the capacity of the lithium ion battery was low and the capacity retention rate for 1000 cycles was low, indicating that the capacity of the lithium ion battery was low and the cycle performance was poor.
The diameter D of single-walled carbon nanotubes affects the capacity and cycle performance of lithium ion batteries. As can be seen from examples 1-1, 1-6 to 1-11, 1-16 and 1-17, the lithium ion battery has higher capacity and higher cycle performance by adjusting the value of D within the scope of the application, which is illustrated by higher capacity and higher capacity retention rate for 1000 cycles. In examples 1-16, the diameter of the single-walled carbon nanotubes was too small, and the single-walled carbon nanotubes had defects and other reaction sites during cycling, resulting in a relatively low capacity retention rate for 1000 cycles of the lithium ion battery.
The values of D3/D1, D4/D2 affect the capacity and cycling performance of the lithium ion battery. As can be seen from examples 1-1 to 1-5, examples 1-12 to 1-15, examples 1-18 and examples 1-19, the lithium ion battery has higher capacity and better cycle performance by controlling the values of D3/D1 and D4/D2 within the scope of the present application, which is illustrated by higher capacity of the lithium ion battery and higher capacity retention rate of 1000 cycles.
Particle size Dv10 of the nickel-cobalt-manganese ternary material and particle size Dv10 of lithium iron manganese phosphate can influence the capacity and cycle performance of the lithium ion battery. As can be seen from examples 1-1 to 1-5, examples 1-12 to 1-15, examples 1-18 and examples 1-19, by adjusting the particle size Dv10 of the nickel-cobalt-manganese ternary material and the particle size Dv10 of the lithium iron manganese phosphate within the scope of the application, the capacity of the lithium ion battery is higher, the capacity retention rate of 1000 cycles is higher, and the lithium ion battery has higher capacity and better cycle performance.
TABLE 2
The mass percentage content W1 of the conductive agent affects the capacity and cycle performance of the lithium ion battery. As can be seen from examples 1-1, 2-1 to 2-4 and 2-9, the lithium ion battery has higher capacity and higher cycle capacity retention rate of 1000 cycles by controlling the mass percent content W1 of the conductive agent within the scope of the application, which indicates that the lithium ion battery has higher capacity and better cycle performance. As is clear from comparative examples 2-1 to 2-4, the conductive agent in the positive electrode material layer is Super P, the mass percentage of the conductive agent is higher, the capacity of the lithium ion battery is lower, the capacity retention rate of 1000 cycles is lower, and the lower capacity and the poorer cycle performance of the lithium ion battery are indicated; as the mass percentage content W1 of the conductive agent increases, the capacity of the lithium ion battery increases.
The mass percent Wa of the nickel-cobalt-manganese ternary material and the mass percent Wb of the lithium iron manganese phosphate can influence the capacity and the cycle performance of the lithium ion battery. As can be seen from examples 1-1, 2-7, 2-8 and 2-10, the lithium ion battery has higher capacity and higher capacity retention rate in 1000 cycles by controlling the mass percent Wa of the nickel-cobalt-manganese ternary material and the mass percent Wb of the lithium iron manganese phosphate within the range of the application, which indicates that the lithium ion battery has higher capacity and better cycle performance.
The mass percentage content W2 of the positive electrode active material and the mass percentage content W3 of the binder affect the capacity, the cycle performance and the internal resistance of the lithium ion battery. As can be seen from examples 1-1, examples 2-5 and examples 2-6, the lithium ion battery has higher capacity and higher cycle performance by controlling the mass percent content W2 of the positive electrode active material and the mass percent content W3 of the binder within the scope of the application, and the capacity retention rate of 1000 cycles is higher.
The foregoing description of the preferred embodiments of the application is not intended to limit the application to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the application are intended to be included within the scope of the application.

Claims (11)

1. A secondary battery comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprises a positive electrode active material and a conductive agent, the positive electrode active material comprises a nickel-cobalt-manganese ternary material and ferric manganese lithium phosphate, the particle size Dv50 of the nickel-cobalt-manganese ternary material is D1 mu m, the particle size Dv50 of the ferric manganese lithium phosphate is D2 mu m, the particle size Dv90 of the nickel-cobalt-manganese ternary material is D3 mu m, the particle size Dv90 of the ferric manganese lithium phosphate is D4 mu m, D1 is not less than or equal to 5.6,0.5 is not more than 4, D3 is not more than 18, and D4 is not more than 10 and not more than 30;
The conductive agent comprises single-walled carbon nanotubes, the length of each single-walled carbon nanotube is L nm, the diameter of each single-walled carbon nanotube is D nm, the length-diameter ratio of each single-walled carbon nanotube is X, X=L/D, X is more than or equal to 1667 and less than or equal to 40000, and L is more than or equal to 10000 and less than or equal to 40000.
2. The secondary battery according to claim 1, wherein 6667.ltoreq.X.ltoreq.40000.
3. The secondary battery according to claim 1 or 2, wherein 20000.ltoreq.l.ltoreq.40000.
4. The secondary battery according to claim 1 or 2, wherein 1.ltoreq.d.ltoreq.6.
5. The secondary battery according to claim 1 or 2, wherein 1.ltoreq.d.ltoreq.3.
6. The secondary battery according to claim 1 or 2, wherein 1.5.ltoreq.d3/d1.ltoreq.3.5, 3.ltoreq.d4/d2.ltoreq.25.
7. The secondary battery according to claim 1 or 2, wherein the nickel-cobalt-manganese ternary material has a particle diameter Dv10 of D5 μm, and the lithium iron-manganese phosphate has a particle diameter Dv10 of D6 μm, 1.8.ltoreq.d5.ltoreq. 2.8,0.2.ltoreq.d6.ltoreq.0.5.
8. The secondary battery according to claim 1, wherein the mass percentage content W1 of the conductive agent is 0.2% to 0.8% based on the mass of the positive electrode material layer.
9. The secondary battery according to claim 1 or 2, wherein the nickel cobalt manganese ternary material has a mass percentage Wa of 35% to 95% and the iron manganese lithium phosphate has a mass percentage Wb of 5% to 65% based on the mass of the nickel cobalt manganese ternary material and the iron manganese lithium phosphate.
10. The secondary battery according to claim 8, wherein the positive electrode material layer further comprises a binder, the positive electrode active material having a mass percentage W2 of 96.8% to 98.8% and the binder having a mass percentage W3 of 1% to 2.4% based on the mass of the positive electrode material layer.
11. An electronic device comprising the secondary battery according to any one of claims 1 to 10.
CN202410508755.6A 2024-04-25 2024-04-25 Secondary battery and electronic device Pending CN118431399A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119480904A (en) * 2024-11-15 2025-02-18 珠海冠宇电池股份有限公司 Positive electrode sheet and lithium ion secondary battery
CN120072849A (en) * 2025-02-21 2025-05-30 珠海冠宇电池股份有限公司 Positive plate and lithium ion secondary battery

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119480904A (en) * 2024-11-15 2025-02-18 珠海冠宇电池股份有限公司 Positive electrode sheet and lithium ion secondary battery
CN120072849A (en) * 2025-02-21 2025-05-30 珠海冠宇电池股份有限公司 Positive plate and lithium ion secondary battery
CN120072849B (en) * 2025-02-21 2025-11-07 珠海冠宇电池股份有限公司 A positive electrode and a lithium-ion secondary battery

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