CN115513515A - Secondary battery and preparation method thereof - Google Patents
Secondary battery and preparation method thereof Download PDFInfo
- Publication number
- CN115513515A CN115513515A CN202211199227.4A CN202211199227A CN115513515A CN 115513515 A CN115513515 A CN 115513515A CN 202211199227 A CN202211199227 A CN 202211199227A CN 115513515 A CN115513515 A CN 115513515A
- Authority
- CN
- China
- Prior art keywords
- active material
- positive
- iron phosphate
- lithium iron
- secondary battery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000002360 preparation method Methods 0.000 title abstract description 44
- 239000002245 particle Substances 0.000 claims abstract description 172
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 99
- 239000007774 positive electrode material Substances 0.000 claims abstract description 77
- 238000005056 compaction Methods 0.000 claims description 30
- 239000003575 carbonaceous material Substances 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 15
- 239000007773 negative electrode material Substances 0.000 claims description 14
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 238000009826 distribution Methods 0.000 abstract description 17
- 239000010410 layer Substances 0.000 description 30
- 239000006258 conductive agent Substances 0.000 description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 19
- 239000006185 dispersion Substances 0.000 description 19
- 238000000034 method Methods 0.000 description 17
- 239000002002 slurry Substances 0.000 description 13
- 239000000463 material Substances 0.000 description 12
- 239000011230 binding agent Substances 0.000 description 10
- 229910002804 graphite Inorganic materials 0.000 description 10
- 239000010439 graphite Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000012546 transfer Methods 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 6
- 238000004537 pulping Methods 0.000 description 6
- 239000000654 additive Substances 0.000 description 5
- 230000000996 additive effect Effects 0.000 description 5
- 239000006183 anode active material Substances 0.000 description 5
- 229910010710 LiFePO Inorganic materials 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000002955 isolation Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 239000006256 anode slurry Substances 0.000 description 3
- 238000007600 charging Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 238000010280 constant potential charging Methods 0.000 description 3
- 239000011267 electrode slurry Substances 0.000 description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000006182 cathode active material Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000008103 glucose Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 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
- 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
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 229910001935 vanadium oxide Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Classifications
-
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1397—Processes of manufacture of 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
- H01M4/58—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
- 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
-
- 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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
-
- 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
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application discloses a secondary battery and a preparation method thereof. The secondary battery comprises a positive pole piece, wherein the positive pole piece comprises a positive current collector and a positive active material layer arranged on the positive current collector, and the positive active material layer contains a positive active material; the positive electrode active material includes lithium iron phosphate particles; with the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer as 100%, 5 μm × 5 μm is one of the unit cross-sectional areas: the number of the lithium iron phosphate particles with the particle size of 0.4-2 mu m accounts for 70-95%. According to the preparation method, the lithium iron phosphate with uniform particle morphology is prepared, the particle size distribution of the lithium iron phosphate is controlled, and the capacity and the cycle performance of the battery can be remarkably improved.
Description
Technical Field
The invention belongs to the field of secondary batteries, and relates to a secondary battery and a preparation method thereof.
Background
Secondary batteries, such as lithium ion batteries, are widely used in consumer electronics, automobiles, electric vehicles, energy storage, and other fields because of their high voltage and energy density characteristics, cleanliness, high efficiency, and no environmental pollution. The lithium iron phosphate anode active material is an ideal anode active material due to low cost, no pollution and good safety performance. However, the lithium iron phosphate positive electrode active material has a problem of low theoretical capacity.
Therefore, it is necessary to provide a positive electrode sheet having a higher energy density.
Disclosure of Invention
An object of the present application is to provide a secondary battery and a method of manufacturing the same.
According to the method, the lithium iron phosphate with uniform particle morphology is prepared, the particle size distribution of the lithium iron phosphate is controlled, and the number proportion distribution condition of the lithium iron phosphate particles under the specific particle size in the positive active material layer is controlled, so that the capacity and the cycle performance of the battery are remarkably improved.
The application provides a secondary battery, which comprises a positive pole piece, wherein the positive pole piece comprises a positive current collector and a positive active material layer arranged on the positive current collector, and the positive active material layer contains a positive active material;
the positive electrode active material includes lithium iron phosphate particles;
the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer is 100%, and 5 μm × 5 μm is one unit cross-sectional area:
the number of the lithium iron phosphate particles with the particle size of 0.4-2 mu m accounts for 75-95%.
In the application, the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer is obtained through a scanning electron microscope test;
the particle size of the lithium iron phosphate particles is 0.4-2 mu m, and the particle size value is measured by CP-SEM and specifically refers to the maximum value of the measurement length of a single particle.
In the above secondary battery, the number of particles having a particle diameter of more than 2 μm is 10% or less, and the number of particles having a particle diameter of 0.4 μm or less and 0.1 μm or more is 15% or less.
In the secondary battery, the surface of the lithium iron phosphate material particles is provided with the carbon material, and the content of the carbon material can be 0.5-2% based on the mass of the positive electrode active material.
In the above secondary battery, the positive electrode active material layer contains an M element containing at least one of Ti, V, and Zr;
the content of the M element may be 100ppm to 3000ppm based on the weight of the positive electrode active material layer.
In the above-described secondary battery, the positive electrode active material particles satisfy at least one of the following characteristics:
(a) The Dv10 of the lithium iron phosphate particles is 0.1-0.5 μm, the Dv50 is 0.7-1.5 μm, and the Dv90 is 1.5-5 μm;
(b) The lithium iron phosphate particles satisfy (Dv 90-Dv 10)/Dv 50=0.1 to 10.
In the application, the shape distribution uniformity of the particles of the positive pole piece manufactured by the lithium iron phosphate particles is improved by adjusting the particle size distribution of the lithium iron phosphate particles.
In the secondary battery, the powder compaction density of the lithium iron phosphate particles under the pressure of 30KN is more than 2.3g/cm 3 When the powder is compacted to less than 2.3g/cm 3 The compaction density of the lithium iron phosphate positive pole piece can be influenced.
In the above secondary battery, the positive current collector is provided with a conductive layer, and the thickness of the conductive layer may be 0.5 to 10 μm.
In the above secondary battery, the positive current collector is provided with a conductive layer, and the thickness of the conductive layer may be 0.5 μm to 3 μm.
In the above secondary battery, the secondary battery further comprises a negative electrode plate, the negative electrode plate comprises a negative current collector and a negative active material layer arranged on the negative current collector, and the specific surface area of the negative active material is recorded as A 1 m 2 (g), specific surface area of the positive electrode active materialIs marked as A 2 m 2 A/g, satisfies 0.05. Ltoreq. A 1 /A 2 ≤0.3。
In the above secondary battery, A is 0.5. Ltoreq. 1 ≤4，9≤A 2 ≤13。
The application also provides an electric device comprising the secondary battery.
The application has the following beneficial effects:
the energy density of the lithium iron phosphate positive pole piece can be remarkably improved by regulating the proportion of the number of lithium iron phosphate particles with the particle size of 0.4-2 mu m in the positive pole piece to the total number of lithium iron phosphate particles in a unit area (5 mu m multiplied by 5 mu m).
Drawings
FIG. 1 is a CP-SEM image of the lithium iron phosphate positive electrode sheet in example 1 of the present invention.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
According to the method, the particle morphology of the lithium iron phosphate material is selected, the particle size distribution of the particles is optimized, and the processing technology of the positive plate is adjusted, so that the quantity proportion distribution condition of the positive plate in the specific particle size of the cross section direction of the positive plate is regulated, and the energy density of the lithium iron phosphate secondary battery is remarkably improved.
The application provides a secondary battery, which comprises a positive pole piece, wherein the positive pole piece comprises a positive current collector and a positive active material layer arranged on the positive current collector, and the positive active material layer contains a positive active material;
the positive electrode active material includes lithium iron phosphate particles;
the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer is 100%, and 5 μm × 5 μm is one unit cross-sectional area:
the number of the lithium iron phosphate particles with the particle size of 0.4-2 mu m accounts for 75% -95%. For example, it may be 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 95%, or a range consisting of any two of these. When the number ratio of the lithium iron phosphate particles with the particle size of 0.4-2 mu m is in the range, the charge transfer sites of the positive active material and the electrolyte interface on the positive pole piece are increased, so that the charge transfer resistance at the interface is reduced; meanwhile, the mixing of the positive active material and the conductive material can be more uniform, the formed conductive network is better, and the circulating capacity retention rate and energy density of the secondary battery can be improved.
In some embodiments of the present application, the lithium iron phosphate particles having a particle size of 0.4 to 2 μm may be present in an amount of 82 to 95%. When the number of the lithium iron phosphate particles with the particle size of 0.4-2 mu m is in the range, the distribution of the positive active material particles in the positive active material layer is more reasonable, the contact area between the particles is larger, the lithium iron phosphate particles have smaller charge transfer resistance and more perfect conductive network, and the comprehensive performance of the battery is better.
In the application, the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer is obtained by a scanning electron microscope test;
the particle size of the lithium iron phosphate particles is 0.4-2 mu m, and the particle size value specifically refers to the maximum value of the measured length of a single particle.
In some embodiments of the present application, the number of particles having a particle size > 2 μm is less than or equal to 10%. For example, it may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, or a range consisting of any two of these. When the number of the particles with the particle size larger than 2 mu m is in the range, the particle size distribution of the positive active material particles can be in a proper range, the dispersion condition among the positive active material particles in the positive active material layer can be in a more reasonable state, the contact points of the conductive material and the positive active material are increased, the transfer of electrons is facilitated, and the secondary battery has higher energy density and better cycle performance.
In some embodiments of the present application, the number of particles having a particle size of > 2 μm is 8% or less. When the number of the particles with the particle size larger than 2 mu m is in the range, the reduction of the utilization rate of the internal space of the positive pole piece, the reduction of the contact area among the particles and the influence on the compaction density of the positive pole piece caused by the accumulation of large particles can be reduced, so that the secondary battery has better comprehensive performance.
In some embodiments of the present application, the number of particles having a particle size > 2 μm of the lithium iron phosphate particles is greater than or equal to 0.5%. When the particle size of the lithium iron phosphate particles is within the above range, the overall performance of the secondary battery is better.
In some embodiments of the present application, the number of particles having a particle size of less than 0.4 μm and greater than or equal to 0.1 μm in the lithium iron phosphate particles is less than or equal to 15%. For example, it may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 15%, or a range consisting of any two of these. When the number of particles with the particle size of less than 0.4 mu m and more than or equal to 0.1 mu m in the lithium iron phosphate particles is in the range, the particle size distribution of the positive active material particles can be in a proper range, the contact surface between the positive active material particles can be increased, the contact points between the conductive material and the positive active material are increased, and the transfer of electrons is facilitated; meanwhile, the number of the lithium iron phosphate particles with the particle size within the range is controlled, so that the side reaction between the electrolyte and the positive active material particles can be reduced, and the secondary battery has higher energy density and better cycle performance.
In some embodiments of the present application, the number of particles having a particle size of less than 0.4 μm and greater than or equal to 0.1 μm in the lithium iron phosphate particles is 1% to 12%.
In some embodiments of the present application, the number of particles having a particle size of less than 0.4 μm and greater than or equal to 0.1 μm in the lithium iron phosphate particles is 2% to 10%. When the number ratio of the particles with the particle size of less than 0.4 mu m and more than or equal to 0.1 mu m in the lithium iron phosphate particles is in the range, the reaction area of the positive active material particles and the electrolyte can be in a proper range, unnecessary side reactions in the secondary battery can be further reduced, and the secondary battery has better comprehensive performance.
In some embodiments of the present application, a carbon material is disposed on a surface of the lithium iron phosphate particles, and the content of the carbon material may be 0.5% to 2% based on the mass of the positive electrode active material. For example, it may be 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, or a range consisting of any two of these. When the content of the carbon material in the positive electrode active material is within the above range, the conductivity of the positive electrode active material can be improved while the influence on the energy density of the secondary battery is small.
In some embodiments of the present application, a carbon material is disposed on a surface of the lithium iron phosphate particles, and the content of the carbon material may be 0.8% to 1.7% based on the mass of the positive electrode active material. When the content of the carbon material is within the above range, the thickness of the conductive layer on the surface of the positive electrode active material particles is within a suitable range, and the conductive network is relatively complete, so that the comprehensive performance of the secondary battery is better.
In some embodiments of the present application, the carbon material has superior electrical conductivity properties, e.g., the carbon material comprises amorphous carbon and/or conductive carbon black.
In some embodiments of the present application, the carbon material particles have a particle size of less than 0.1 times the particle size of lithium iron phosphate. When the particle size of the carbon material is within the range, the positive active material particles can be better coated, so that the conductive network on the surface of the positive active material particles is more complete, the conductive network which can be formed by the positive pole piece is diversified, and the improvement of the comprehensive performance of the secondary battery is facilitated.
In some embodiments of the present application, the positive electrode active material layer includes an M element including at least one of Ti, V, or Zr. The M element can increase the structural stability of the positive active material, and can improve the conductivity of the positive pole piece, so that the performance of the secondary battery is better.
In some embodiments of the present application, the positive active material layer includes an M element including Ti.
In some embodiments of the present application, the content of the M element may be 100ppm to 3000ppm based on the weight of the cathode active material layer. For example, the concentration may be 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1400ppm, 1500ppm, 1540ppm, 1568ppm, 1578ppm, 1620ppm, 1637ppm, 1659ppm, 1673ppm, 1697ppm, 1700ppm, 1701ppm, 1900ppm, 2000ppm, 2300ppm, 2500ppm, 2800ppm, 3000ppm or a range consisting of any two of these.
In some embodiments of the present application, the content of the M element may be 500ppm to 2500ppm based on the weight of the positive electrode active material layer.
In some embodiments of the present application, the lithium iron phosphate particles Dv10 are 0.1 μm to 0.5 μm. For example, it may be 0.1. Mu.m, 0.15. Mu.m, 0.2. Mu.m, 0.25. Mu.m, 0.3. Mu.m, 0.37. Mu.m, 0.38. Mu.m, 0.39. Mu.m, 0.35. Mu.m, 0.4. Mu.m, 0.41. Mu.m, 0.45. Mu.m, 0.5. Mu.m, or a range of any two of them.
In some embodiments of the present application, the lithium iron phosphate particles Dv50 are 0.7 μm to 1.5 μm. For example, it may be 0.7. Mu.m, 0.75. Mu.m, 0.8. Mu.m, 0.85. Mu.m, 0.9. Mu.m, 0.95. Mu.m, 1. Mu.m, 1.08. Mu.m, 1.07. Mu.m, 1.1. Mu.m, 1.11. Mu.m, 1.13. Mu.m, 1.2. Mu.m, 1.3. Mu.m, 1.5. Mu.m, 1.51. Mu.m, or a combination of any two thereof.
In some embodiments of the present application, the lithium iron phosphate particles Dv90 are 1.5 μm to 5 μm. For example, it may be 1.5. Mu.m, 1.9. Mu.m, 2. Mu.m, 2.5. Mu.m, 3. Mu.m, 3.2. Mu.m, 3.21. Mu.m, 3.25. Mu.m, 3.28. Mu.m, 3.30. Mu.m, 3.34. Mu.m, 3.35. Mu.m, 3.38. Mu.m, 3.40. Mu.m, 3.5. Mu.m, 3.8. Mu.m, 4. Mu.m, 4.94. Mu.m, 1.1. Mu.m, 1.2. Mu.m, 1.3. Mu.m, 1.5. Mu.m, or a range of any two of them.
When the volume particle size distribution of the positive electrode active material is within the above range, the particle distribution of the positive electrode active material in the positive electrode sheet can be in a more appropriate state.
In the application, dv10, dv50, and Dv90 of the lithium iron phosphate particles may be measured by a laser particle sizer, and the dispersing agent is deionized water.
In some embodiments of the present application, the lithium iron phosphate particles satisfy (Dv 90-Dv 10)/Dv 50=0.1 to 10. For example, the range may be 0.1, 0.5, 1, 1.5, 1.8, 2.0, 2.01, 2.2, 2.5, 2.60, 2.66, 2.68, 2.69, 2.74, 2.75, 2.8, 2.88, 3.0, 3.2, 3.5, 3.79, 3.8, 4.0, 4.04, 4.5, 4.8, 5, 6, 7, 8, 10 or any two of these. The shape distribution of the particles of the positive pole piece manufactured by the lithium iron phosphate is improved to be uniform by adjusting the particle size distribution of the lithium iron phosphate particles. The secondary battery has better cycle performance and higher energy density.
In some embodiments of the present application, the lithium iron phosphate particles satisfy the range of (Dv 90-Dv 10)/Dv 50 of 1.8 to 4.5.
In some embodiments of the present application, the lithium iron phosphate particles have a powder compaction density of greater than 2.3g/cm at a pressure of 30KN 3 . In some embodiments of the present application, the lithium iron phosphate particles have a powder compaction density greater than 2.35g/cm at a pressure of 30KN 3 . In some embodiments of the present application, the lithium iron phosphate particles have a powder compaction density of less than or equal to 3.5g/cm at a pressure of 30KN 3 . In some embodiments of the present application, the lithium iron phosphate particles have a powder compaction density of less than or equal to 3.0g/cm at a pressure of 30KN 3 . In some embodiments of the present application, the powder compaction density of the lithium iron phosphate particles under a 30KN pressure is 2.3 to 3.0g/cm 3 . In some embodiments of the present application, the powder compaction density of the lithium iron phosphate particles under a 30KN pressure is 2.35 to 2.9g/cm 3 . In some embodiments of the present application, the powder compaction density of the lithium iron phosphate particles under a 30KN pressure is 2.35 to 2.8g/cm 3 . In some embodiments of the present application, the powder compaction density of the lithium iron phosphate particles under a pressure of 30KN is 2.35 to 2.65g/cm 3 . When the powder compaction density of the lithium iron phosphate particles is in the range, the prepared positive pole piece can be higher in compaction density, so that the secondary battery has better cycle performance and higher energy density.
In the above secondary battery, the positive current collector is provided with a conductive layer, and the thickness of the conductive layer may be 0.5 μm to 10 μm.
In the above secondary battery, the positive current collector is provided with a conductive layer, and the thickness of the conductive layer may be 0.5 μm to 3 μm. When the thickness of the conductive layer is in the above range, the conductive capability of the positive pole piece can be further improved, and the energy density of the secondary battery is in a better range.
In the above secondary battery, the secondary battery further comprises a negative electrode plate, the negative electrode plate comprises a negative current collector and a negative active material layer arranged on the negative current collector, the specific surface area of the negative active material is marked as A 1 m 2 The specific surface area of the positive electrode active material is marked as A 2 m 2 A/g, satisfies 0.05. Ltoreq. A 1 /A 2 Less than or equal to 0.3. For example, it may be 0.027, 0.05, 0.07, 0.082, 0.09, 0.095, 0.096, 0.097, 0.098, 0.099, 0.1, 0.103, 0.109, 0.13, 0.15, 0.159, 0.17, 0.177, 0.2, 0.22, 0.211, 0.239, 0.25, 0.265, 0.28, 0.3, 0.353, or a range consisting of any two of these numbers. When A is 1 /A 2 Within the above range, the reaction efficiency of the positive electrode active material and the negative electrode active material can be better matched in the battery charging and discharging process, so that unnecessary side reactions are reduced, and the overall performance of the battery is better.
In the above secondary battery, A is 0.5. Ltoreq. 1 Less than or equal to 4. For example, it may be 0.5, 1.0, 1.1, 1.5, 1.7, 1.8, 2.0, 2.3, 2.5, 2.7, 3.0, 3.2, 3.5, 4 or a range consisting of any two of these.
In the above secondary battery, A is 1.5. Ltoreq. 1 ≤4。
In the above secondary battery, 9. Ltoreq. A 2 Less than or equal to 13. For example, the range may be 9, 9.5, 10, 10.1, 10.5, 10.7, 11, 11.1, 11.2, 11.3, 11.5, 11.6, 12, 12.5, 12.8, 13 or any two of these.
The application also provides an electric device comprising the secondary battery.
In the secondary battery, the positive pole piece comprises the following components in percentage by mass, and the total amount is 100%:
96% -99% of the positive active material layer;
1% -2% of the conductive agent;
1% -2% of the binder.
In the above secondary battery, the conductive agent may comprise the following components in percentage by mass:
80-90% of conductive carbon black SP and 10-20% of conductive graphite.
In the application, a conductive agent with better conductivity is selected to improve the conductivity; the consumption of the conductive agent and the binder is reduced, and the compaction density of the lithium iron phosphate positive plate is improved, so that the energy density of the secondary battery can be improved.
The application also provides a preparation method of the positive pole piece in the secondary battery, which comprises the following steps:
mixing the positive electrode active material, the conductive agent and the binder according to a required proportion, and adding a solvent; then transferring the slurry into a vacuum stirrer for low-speed dispersion and high-speed dispersion, and performing vacuum reversal defoaming after dispersion is finished to obtain anode slurry; uniformly coating the two sides of the positive electrode slurry on a substrate, drying, and then carrying out cold pressing and slitting to obtain the positive electrode piece;
wherein the solvent comprises N-methylpyrrolidone;
the rotating speed of the low-speed dispersion can be 500 r/min-2500 r/min, for example, 500 r/min-800 r/min, 800 r/min-2500 r/min, 600-2300 r/min, 700 r/min-2000 r/min, 700 r/min-1800 r/min, 500 r/min-1000 r/min or 500 r/min-1500 r/min; the time may be 0.5 to 4 hours, for example, 0.5 to 3.5 hours, 0.5 to 3 hours, 0.5 to 2.5 hours, 0.5 to 2 hours, 0.5 to 1.5 hours, 1 to 2.5 hours, and 1 to 2 hours.
The high-speed dispersion rotating speed is 2500-5000 r/min, for example, 2500-3500 r/min, 3500-5000 r/min, 2500-4000 r/min, 2800-3800 r/min, 2800-3500 r/min or 3000-4500 r/min; the time is 3 to 8 hours, specifically 3 to 4.5 hours, 4.5 to 8 hours, 4.5 to 5.5 hours, 3.5 to 7 hours, 4.0 to 7.5 hours or 4 to 6 hours; the rotating speed of the slurry during dispersion is increased, so that the conductive agent and the binder are fully and uniformly dispersed;
the viscosity of the positive electrode slurry can be 3000-5000 mPas;
the substrate is aluminum foil or carbon-coated aluminum foil, and the drying temperature can be 100-120 ℃.
Example 1
(1) The preparation method of the positive active material comprises the following specific steps:
a) Firstly, weighing anhydrous iron phosphate and lithium carbonate according to the mol ratio of 1. B) Transferring the ball-milled slurry into a sand mill for sand milling, and controlling the particle diameter D of a sand milling product V 50 is 0.8 μm. C) And adding 5wt% of glucose into the sand-milled slurry as an organic carbon source, keeping the temperature of the slurry at 80-85 ℃ (specifically 80 ℃), slowly stirring for 2h, and spray-drying to obtain carbon-coated lithium iron phosphate precursor powder. D) Transferring the precursor powder into a sintering furnace, heating to 380 ℃ from room temperature at a heating rate of 10 ℃/min under the protection of nitrogen, and preserving heat for 4 hours; then sintering for 10 hours at the temperature rising rate of 10 ℃/min to 700 ℃, and then naturally cooling to obtain sintered powder. E) Pulverizing the sintered material by jet mill, and controlling the pulverizing particle diameter D V 10 in the range of 0.41 μm; d V The 50 particle size range is 1.08 mu m; d V The particle size of 90 is 3.3 μm, and then the lithium iron phosphate positive active material coated with carbon (the carbon content of the coating on the surface of the lithium iron phosphate material is 1.35%) is obtained by sieving and removing iron with current.
(2) Preparing a positive pole piece:
a) The particle size distribution range (D) V 10 is 0.41 μm, D V 50 is 1.08 μm, D V 90 is 3.3 μm) of a lithium iron phosphate positive electrode active material (specific surface area 11.3 m) 2 (iv)/g), a binder polyvinylidene fluoride (PVDF for short), a conductive agent SP, and conductive graphite (80 wt%:20 wt%) according to a mass ratio of 97:1.5, adding solvent N-methylpyrrolidone NMP; b) Then transferring the slurry into a vacuum stirrer to perform low-speed dispersion (the rotating speed is 800r/min, the dispersion time is 0.5 h) and high-speed dispersion (the rotating speed is 3500r/min, the dispersion time is 4.5 h) respectively, and performing vacuum inversion defoaming after the dispersion is finished to finally obtain the anode slurry with the solid content of 56% and the viscosity of 4200 Pa.s; c) The anode slurry is homogenizedCoated on both surfaces of a 14 μm carbon-coated aluminum foil (with a thickness of 1 μm each of the double-sided carbon-containing coating layers); d) Drying the coated pole piece by an oven at 100-120 ℃; e) And obtaining the positive pole piece through cold pressing and slitting.
(3) Preparing a negative pole piece:
graphite (specific surface area 1.1 m) as a negative electrode active material was added 2 The method comprises the following steps of (1)/g) mixing a thickening agent sodium carboxymethyl cellulose, an adhesive styrene butadiene rubber and a conductive agent acetylene black according to a mass ratio of 97; uniformly coating the negative electrode slurry on a copper foil with the thickness of 6 mu m; and transferring the coated pole piece to a 120 ℃ oven for drying, and then carrying out cold pressing and slitting to obtain the negative pole piece.
(4) Preparing an electrolyte:
the organic solvent is a mixed solution containing Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20. At water content<In a 10ppm argon atmosphere glove box, fully dried LiPF 6 And dissolving the lithium salt in an organic solvent, and uniformly mixing to obtain the electrolyte. Wherein the concentration of the lithium salt is 1mol/L.
(5) Preparing an isolating membrane:
a polypropylene isolating membrane with the thickness of 12 mu m is selected.
(6) Preparing a battery:
the positive pole piece, the isolation film and the negative pole piece are sequentially stacked to enable the isolation film to be positioned between the positive pole piece and the negative pole piece to play a role of isolation, then the positive pole piece, the isolation film and the negative pole piece are wound into a square bare cell and then are placed into a shell, then the shell is baked at 80 ℃ to remove water, corresponding non-aqueous electrolyte is injected and sealed, and the finished battery is obtained after the working procedures of standing, hot cold pressing, formation, clamping, capacity grading and the like.
The CP-SEM of the lithium iron phosphate positive electrode piece in example 1 of the invention is shown in FIG. 1.
As can be seen from figure 1, the lithium iron phosphate material of the invention has uniform and moderate particle size distribution, and the LiFePO with the particle size of 0.4-2 μm per unit area in the unit area of the positive pole piece prepared by the method 4 The total number of the positive electrode plate accounts for 93 percent, and the positive electrode plateHas a compacted density of 2.71g/cm 3 。
Example 2
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) The conductive agent is selected as the conductive agent SP in the preparation process of the positive pole piece.
Example 3
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) Conductive agent SP and conductive graphite (90 wt%:10 wt%) are selected in the preparation process of the positive pole piece.
Example 4
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) In the preparation process of the positive pole piece, a conductive agent SP and conductive graphite (70 wt%:30 wt%) are selected.
Example 5
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) The mass ratio of the lithium iron phosphate positive active material, the binder and the conductive agent added in the preparation process of the positive pole piece is 96:2:2.
example 6
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) The mass ratio of the lithium iron phosphate positive active material, the binder and the conductive agent added in the preparation process of the positive pole piece is 98:1:1.
example 7
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) The content of the doping additive in the preparation process of the positive active material; and (2) the particle size range of the lithium iron phosphate material is selected in the preparation process of the positive pole piece (Dv 10 is 0.15 μm, dv50 is 1.11 μm, and Dv90 is 3.35 μm).
Example 8
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) The content of the doping additive in the preparation process of the positive active material; and (2) the particle size range of the lithium iron phosphate material (Dv 10 is 0.38 μm, dv50 is 1.13 μm, dv90 is 4.94 μm) is selected in the preparation process of the positive pole piece.
Example 9
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) The content of the doping additive in the preparation process of the positive active material; and (2) the particle size range of the lithium iron phosphate material is selected in the preparation process of the positive pole piece (Dv 10 is 0.37 μm, dv50 is 1.51 μm, and Dv90 is 3.40 μm).
Example 10
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (2) The particle size range of the lithium iron phosphate material (Dv 10 is 0.35 μm, dv50 is 0.8 μm, dv90 is 3.38 μm) is selected in the preparation process of the positive pole piece.
Example 11
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (3) Selecting a specific surface area of 1.8m 2 Graphite as a negative electrode active material per gram.
Example 12
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (3) Selecting a specific surface area of 0.3m 2 Graphite as a negative electrode active material per gram.
Example 13
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) In the preparation process of the anode active material, 0.2wt% of vanadium oxide is selected as an ion doping additive.
Example 14
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) In the preparation process of the anode active material, 0.2wt% of zirconia is selected as an ion doping additive.
Examples 15 to 18
The preparation method and conditions are the same as those in example 1, except that: (2) Preparing the positive pole piece, namely B), changing the stirring time, the rotating speed and the viscosity of the discharged slurry in the pulping process; wherein, the dispersion time of the high-speed dispersion stage in the pulping process of the embodiment 15 is 2.5h; the rotating speed of the high-speed dispersion stage in the pulping process of the embodiment 16 is 2500r/min; example 17 pulping process the pulp was shipped at a viscosity of 3000mpa.s; example 18 pulping process the viscosity of the pulp shipment was 6000mpa.s; the number ratio of the positive electrode active material particles having a particle diameter of 0.4 to 2 μm was made different as shown in table 2.
Examples 19 to 23
The preparation method and conditions are the same as those in example 1, except that: the surface areas of the negative electrode active materials were different as shown in table 1.
Examples 24 to 26
The preparation method and conditions are the same as those in example 1, except that: in the preparation process of the positive active material, the addition amounts of organic carbon sources are different, and 2wt%,6wt% and 7wt% of glucose are respectively and sequentially added, so that the contents of active carbon materials on the surface of the active material are different.
Comparative example 1
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: (1) In the preparation process of the positive active material, the particle size of the crushed particles is not controlled in the step E), and the lithium iron phosphate positive active material with non-uniform particle size is prepared.
Comparative example 2
The preparation method and conditions are the same as those in the embodiment 1 of the invention, except that: the high-speed dispersion rate of the slurry in the step (2) -B) is 2000r/min.
The results of the performance tests of the above examples and comparative examples are as follows:
LiFePO with unit area particle size of 0.4-2 mu m in pole piece CP-SEM 4 The quantity estimation method of (2) is a statistical average method, and specifically comprises the following steps: randomly selecting CP-SEM pictures at multiple positions of the lithium iron phosphate positive pole piece, randomly calibrating 5 groups of square lattices with the size of 5 microns multiplied by 5 microns according to a corresponding scale of the SEM pictures, calculating the total number of particles (containing particles with square edges) in the square lattices to be N, calculating the number of particles with the size of 0.4-2 microns in the square lattices to be N, and then obtaining LiFePO with the particle size of 0.4-2 microns per unit area in the CP-SEM pictures 4 The ratio of the number of the N/N multiplied by 100 percent. Then taking the average value of the number ratio of the lithium iron phosphate with the particle size of 0.4-2 mu m in unit area in 5 square lattices to obtain the number ratio of the lithium iron phosphate with the particle size of 0.4-2 mu m of CP-SEM in the pole piece。
The test method comprises the following steps:
1/3C first discharge gram capacity:
1. adjusting the temperature of the incubator to 25 ℃, standing for 2h
2.0.33C to 3.65V, followed by constant voltage charging to 0.05C cutoff current
3. Standing for 5min
4.0.33C to 2.5V
5. Standing for 5min
Cycle capacity retention ratio:
1. adjusting the temperature of the incubator to 25 ℃, standing for 2h
2.0.33C to 3.65V, followed by constant voltage charging to 0.05C cutoff current
3. Standing for 5min
4.0.33C to 2.5V
5. Standing for 5min
6.1C constant current charging to 3.65V followed by constant voltage charging to 0.05C cutoff
7. Standing for 5min
Constant current discharging at 8.1 deg.C to 2.5V
9. Standing for 5min
10. Repeating the steps of 6 to 9 until 4000 cycles.
Estimation of the actual energy density:
fully charging the batteries prepared in the examples and the comparative examples at a rate of 1C at 25 ℃, discharging at a rate of 1C, and recording the actual discharge energy at the moment; the cell was weighed at 25 ℃ using an electronic scale; the ratio of the actual 1C discharge energy of the battery to the weight of the battery is the actual energy density of the battery.
Wherein the actual energy density is less than 80% of the target energy density, and the actual energy density of the battery is considered to be very low; the actual energy density is greater than or equal to 80% of the target energy density and less than or equal to 95% of the target energy density, and the actual energy density of the battery is considered to be lower; when the actual energy density is greater than or equal to 95% of the target energy density and less than 105% of the actual energy density, the actual energy density of the battery is considered to be moderate; when the actual energy density is not less than 105% of the target energy density and less than 120% of the target energy density, the actual energy density of the battery is considered to be high; when the actual energy density is 120% or more of the target energy density, the actual energy density of the battery is considered to be very high.
The test results are shown in tables 1 and 2.
TABLE 1 parameters of the examples and comparative examples
TABLE 2 Performance test of examples and comparative examples
From the data in tables 1 and 2, liFePO was obtained 4 The compacted density value of the pole piece is related to the ratio of the number of the lithium iron phosphate with the unit area particle size of 0.4-2 mu m in the pole piece to the total number. On one hand, the increase of the compaction density of the pole piece reduces charge transfer sites on an interface with the electrolyte, so that the charge transfer resistance at the interface is increased, and the influence on the exertion of the specific capacity of the lithium iron phosphate material can be properly reduced. By LiFePO 4 Adjusting the formula of the pole piece, optimizing the pulping process, improving the conductive network structure of the lithium iron phosphate to properly promote high compaction of LiFePO 4 The specific capacity of the pole piece. In addition, by matching the specific surface area of the anode active material with that of the cathode active material, the capacity retention rate of the cycle can be further improved.
From examples 1 to 4, the compaction density of the positive electrode sheet can be significantly changed by adjusting the proportion of the conductive agent. Specifically, the specific surface area of the SP is large, so that the increase of the compacted density of the pole piece is not facilitated, the SP content is high, the dispersibility of the slurry is poor, the dispersibility effect of lithium iron phosphate particles is poor, the number of particles of 0.2-4 mu m in unit area is reduced, the compacted density of the pole piece is slightly reduced, the electronic conductive network is poor, and the electrical property is poor; the proportion of the conductive graphite is too large, the improvement of an electronic conductive network is small, the improvement of the electrical property is limited, the dispersion of the slurry is poor, the dispersion effect of lithium iron phosphate particles is slightly reduced, the number of particles with the particle size of 0.2-4 mu m in unit area is reduced, and the compacted density of the pole piece is slightly reduced; therefore, the proportion of the conductive agent SP is properly reduced, the proportion of the conductive graphite is improved, and on one hand, the compaction density of the pole piece can be properly improved; on the other hand, the mixed use of SP and conductive graphite can optimize the conductive network structure of lithium iron phosphate so as to properly improve the specific capacity of the high-compaction-density pole piece. Thus, the preferred ratio of the selected conductive agents in the present application is shown to be beneficial in increasing the compaction density of the pole piece.
From examples 1, 5 and 6, varying the positive pole piece formulation can affect the compaction density of the positive pole piece. Specifically, the pole piece compaction density of less binder and conductive agent can be obviously improved, but less conductive agent can affect the conductive network structure of the lithium iron phosphate pole piece, and less binder can cause the risk of stripping a current collector of an active material in the repeated charging and discharging process, so that the capacity retention rate is lower. Therefore, the formula of the pole piece material selected by the application is favorable for improving the compaction density of the pole piece.
From examples 1, 7 to 10 and comparative example 1, liFePO 4 The particle size distribution is too wide, too narrow or uneven, which obviously results in the proportion of the particle size of 0.4-2 mu m of lithium iron phosphate in unit area, thereby reducing the compaction density of the pole piece, and therefore, the LiFePO of the application is demonstrated 4 The positive pole piece prepared by particle size adjustment has high compaction density and high energy density.
From examples 11, 12, and 19 to 23, it is seen that the specific surface areas of different negative electrode active materials have little influence on the first discharge gram capacity of the whole battery, and the negative electrode active material with a larger specific surface area can improve the cycle capacity retention rate, but the excessively high specific surface area easily causes the non-uniform dispersion in the slurry preparation process, and can adversely affect the cycle capacity retention rate. When the ratio of the specific surface area of the negative active material to the specific surface area of the positive active material is in the range of 0.05-0.3, the comprehensive performance of the battery is better.
From examples 13 and 14, different M elements have a slight influence on the compaction of the positive electrode plate, wherein M is Ti element, the positive electrode plate has the highest compaction density, and the corresponding electrical property test shows the best performance.
In examples 1 and 24 to 26, too high or too low a content of the surface carbon material in the positive electrode active material was not favorable for the exertion of the actual energy density of the battery.
From examples 1, 15 to 18 and comparative example 2, the dispersing speed and stirring strength of the slurry in the slurry preparation process are proper, so that the active material, the conductive agent and the binder in the lithium iron phosphate pole piece are fully and uniformly dispersed, and the compaction density of the lithium iron phosphate pole piece can be improved. Therefore, the process conditions in the optimized preparation method are favorable for improving the compaction density of the pole piece.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The secondary battery comprises a positive pole piece, and is characterized in that the positive pole piece comprises a positive current collector and a positive active material layer arranged on the positive current collector, wherein the positive active material layer contains a positive active material;
the positive electrode active material includes lithium iron phosphate particles;
with the total number of the lithium iron phosphate particles per unit cross-sectional area in the positive electrode active material layer as 100%, 5 μm × 5 μm is one of the unit cross-sectional areas:
the number of the lithium iron phosphate particles with the particle size of 0.4-2 mu m accounts for 75-95%.
2. The secondary battery according to claim 1, wherein the number of particles having a particle diameter of > 2 μm is 10% or less, and the number of particles having a particle diameter of 0.4 μm or less and 0.1 μm or more is 15% or less.
3. The secondary battery according to claim 1 or 2, wherein the lithium iron phosphate particles have a carbon material on the surface thereof, and the content of the carbon material is 0.5% to 2% based on the mass of the positive electrode active material.
4. The secondary battery according to any one of claims 1 to 3, wherein the positive electrode active material layer contains an M element containing at least one of Ti, V, or Zr;
the content of the M element is 100ppm to 3000ppm based on the weight of the positive electrode active material layer.
5. The secondary battery according to any one of claims 1 to 4, wherein the positive electrode active material particles satisfy at least one of the following characteristics:
(a) The Dv10 of the lithium iron phosphate particles is 0.1-0.5 μm, the Dv50 is 0.7-1.5 μm, and the Dv90 is 1.5-5 μm;
(b) The lithium iron phosphate particles satisfy (Dv 90-Dv 10)/Dv 50=0.1 to 10.
6. According to claimThe secondary battery is characterized in that the powder compaction density of the lithium iron phosphate particles under the pressure of 30KN is more than 2.3g/cm 3 。
7. The secondary battery according to claim 1, wherein a conductive layer is provided on the positive electrode current collector, and the thickness of the conductive layer is 0.5 to 10 μm.
8. The secondary battery of claim 1, further comprising a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the specific surface area of the negative electrode active material is marked as A 1 m 2 (g), the specific surface area of the positive electrode active material is recorded as A 2 m 2 A/g, satisfies 0.05. Ltoreq. A 1 /A 2 ≤0.3。
9. The secondary battery according to claim 8, wherein 0.5. Ltoreq. A 1 ≤4，9≤A 2 ≤13。
10. An electric device comprising the secondary battery according to any one of claims 1 to 9.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211199227.4A CN115513515B (en) | 2022-09-29 | 2022-09-29 | Secondary battery and preparation method thereof |
| PCT/CN2022/139492 WO2024066071A1 (en) | 2022-09-29 | 2022-12-16 | Secondary battery and preparation method therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211199227.4A CN115513515B (en) | 2022-09-29 | 2022-09-29 | Secondary battery and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115513515A true CN115513515A (en) | 2022-12-23 |
| CN115513515B CN115513515B (en) | 2023-12-29 |
Family
ID=84509139
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211199227.4A Active CN115513515B (en) | 2022-09-29 | 2022-09-29 | Secondary battery and preparation method thereof |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN115513515B (en) |
| WO (1) | WO2024066071A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116259736A (en) * | 2023-05-15 | 2023-06-13 | 宁德时代新能源科技股份有限公司 | Positive electrode active material, preparation method thereof, positive electrode plate, secondary battery and power utilization device |
| CN117254129A (en) * | 2023-11-17 | 2023-12-19 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111082052A (en) * | 2019-12-30 | 2020-04-28 | 山东精工电子科技有限公司 | Preparation method of high-compaction lithium iron phosphate material with adjustable particle size |
| CN113428849A (en) * | 2021-06-16 | 2021-09-24 | 张静 | Modified lithium iron phosphate cathode material and preparation method and application thereof |
| CN113451548A (en) * | 2020-03-25 | 2021-09-28 | 比亚迪股份有限公司 | Lithium iron phosphate positive plate, preparation method thereof and lithium iron phosphate lithium ion battery |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100385713C (en) * | 2005-11-30 | 2008-04-30 | 重庆大学 | Method for preparing ferrous lithium phosphate |
| CN112909238B (en) * | 2018-12-29 | 2022-04-22 | 宁德时代新能源科技股份有限公司 | Positive active material, positive pole piece and electrochemical energy storage device |
| EP4229689A1 (en) * | 2020-09-18 | 2023-08-23 | EV Metals UK Limited | Cathode material |
-
2022
- 2022-09-29 CN CN202211199227.4A patent/CN115513515B/en active Active
- 2022-12-16 WO PCT/CN2022/139492 patent/WO2024066071A1/en unknown
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111082052A (en) * | 2019-12-30 | 2020-04-28 | 山东精工电子科技有限公司 | Preparation method of high-compaction lithium iron phosphate material with adjustable particle size |
| CN113451548A (en) * | 2020-03-25 | 2021-09-28 | 比亚迪股份有限公司 | Lithium iron phosphate positive plate, preparation method thereof and lithium iron phosphate lithium ion battery |
| CN113428849A (en) * | 2021-06-16 | 2021-09-24 | 张静 | Modified lithium iron phosphate cathode material and preparation method and application thereof |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116259736A (en) * | 2023-05-15 | 2023-06-13 | 宁德时代新能源科技股份有限公司 | Positive electrode active material, preparation method thereof, positive electrode plate, secondary battery and power utilization device |
| CN116259736B (en) * | 2023-05-15 | 2023-11-07 | 宁德时代新能源科技股份有限公司 | Positive electrode active material, preparation method thereof, positive electrode plate, secondary battery and power utilization device |
| CN117254129A (en) * | 2023-11-17 | 2023-12-19 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2024066071A1 (en) | 2024-04-04 |
| CN115513515B (en) | 2023-12-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10868308B2 (en) | Cathode slurry for lithium ion battery | |
| US9692041B2 (en) | Lithium battery and method of preparing cathode active material for the lithium battery | |
| US10727489B2 (en) | Anode slurry for lithium ion battery | |
| CN115513515B (en) | Secondary battery and preparation method thereof | |
| CN112542589B (en) | Preparation method, product and application of positive electrode prelithiation material | |
| CN114824269B (en) | Composite positive electrode material, preparation method and application thereof, sodium ion battery pack and equipment | |
| CN109461880A (en) | Negative pole piece and battery | |
| WO2014071724A1 (en) | Lithium-rich anode material, lithium battery anode, and lithium battery | |
| CN113517423A (en) | Positive electrode material, preparation method thereof, pole piece and preparation method thereof | |
| WO2024066070A1 (en) | Secondary battery | |
| CN114261995B (en) | Positive electrode active material, preparation method and application thereof | |
| CN115995548A (en) | Lithium cobalt oxide positive electrode material and preparation method thereof | |
| CN115312684B (en) | Positive pole piece and battery | |
| CN114497524B (en) | Preparation method of high-compaction high-cycle ternary positive electrode and lithium secondary battery | |
| CN116190660B (en) | Adhesive, preparation method and application thereof, silicon-based negative electrode and preparation method thereof | |
| CN114665072B (en) | Ternary material and application thereof | |
| CN116387496B (en) | Secondary battery positive electrode material, secondary battery positive electrode plate and secondary battery | |
| CN113471401B (en) | High-safety high-load lithium ion electrode plate and manufacturing method thereof | |
| CN116487525B (en) | Positive plate and battery containing same | |
| CN114665065B (en) | Positive electrode plate and preparation method and application thereof | |
| CN115084440B (en) | Low-impedance positive electrode plate and preparation method and application thereof | |
| CN117766736A (en) | Positive electrode active material and lithium ion battery | |
| CN117976849A (en) | Titanium modified lithium iron manganese phosphate base material and preparation method and application thereof | |
| CN117080436A (en) | Lithium iron phosphate positive electrode material, and preparation method and application thereof | |
| CN116705980A (en) | Thick positive plate, preparation method thereof and secondary battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| CB02 | Change of applicant information |
Address after: 518100, 1st to 2nd floors, Building A, Xinwangda Industrial Park, No. 18 Tangjia South Road, Gongming Street, Guangming New District, Shenzhen, Guangdong Province Applicant after: Xinwangda Power Technology Co.,Ltd. Address before: 518108 Floor 1-2, Building A, Xinwangda Industrial Park, No. 18 Tangjianan Road, Gongming Street, Guangming New District, Shenzhen, Guangdong, China Applicant before: SUNWODA ELECTRIC VEHICLE BATTERY Co.,Ltd. |
|
| CB02 | Change of applicant information | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |