CN116130786A - Secondary battery, preparation method thereof and power utilization device - Google Patents
Secondary battery, preparation method thereof and power utilization device Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 12
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 25
- 239000011248 coating agent Substances 0.000 claims description 53
- 238000000576 coating method Methods 0.000 claims description 53
- 239000000758 substrate Substances 0.000 claims description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 17
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 10
- 239000011230 binding agent Substances 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 10
- 239000006258 conductive agent Substances 0.000 claims description 10
- 239000002270 dispersing agent Substances 0.000 claims description 10
- 239000004698 Polyethylene Substances 0.000 claims description 9
- 239000011888 foil Substances 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 9
- 229920000573 polyethylene Polymers 0.000 claims description 9
- 239000004743 Polypropylene Substances 0.000 claims description 7
- -1 polypropylene Polymers 0.000 claims description 7
- 229920001155 polypropylene Polymers 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- 239000011889 copper foil Substances 0.000 claims description 6
- 229910002804 graphite Inorganic materials 0.000 claims description 6
- 239000010439 graphite Substances 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 5
- 238000009826 distribution Methods 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- 229910010293 ceramic material Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 230000001186 cumulative effect Effects 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 7
- 239000007773 negative electrode material Substances 0.000 description 10
- 239000007774 positive electrode material Substances 0.000 description 10
- 239000010410 layer Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- 239000002033 PVDF binder Substances 0.000 description 4
- 229910021383 artificial graphite Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 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
- 239000011149 active material Substances 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920000447 polyanionic polymer Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 1
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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
- H01M10/058—Construction or manufacture
-
- 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
-
- 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
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
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- 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)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a secondary battery, a preparation method thereof and an electric device, and relates to the technical field of batteries. The volume energy density of the lithium iron phosphate battery, the D90 granularity of the lithium iron phosphate material, the surface density of the positive electrode plate and the thicknesses of the positive electrode current collector, the negative electrode current collector and the isolating film are limited to meet the specific relation of the cell design, so that the volume energy density of the lithium iron phosphate battery can be remarkably improved, and the battery has better cycle life.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a secondary battery, a preparation method thereof and an electric device.
Background
The lithium battery using the lithium iron phosphate as the positive electrode material has the advantages of lower cost, good safety and reliability, ultra-long cycle life, no noble metal ions, environmental protection and the like, and is widely applied at present. However, in terms of energy density, the lithium iron phosphate positive electrode material has lower theoretical capacity (about 170 mAh/g) and lower corresponding working voltage (about 3.4V), and the true density of the material is only 3.6g/cm 3 The above three-point short plate results in a relatively low volumetric energy density of its cells, typically below 420 Wh/L.
Because the gram capacity of the material of the positive electrode active substance of the lithium iron phosphate battery is relatively fixed, the energy density of the material needs to be improved, and the capacity of the negative electrode material can be generally improved, for example, in a traditional lithium battery with the positive electrode of lithium iron phosphate and the negative electrode of graphite, a part of high-capacity silicon negative electrode or silicon-oxygen negative electrode is added into the negative electrode. However, the silicon negative electrode or the silicon oxygen negative electrode material has lower primary efficiency than graphite and higher material cost than artificial graphite, so that the cost of the integrated battery is increased to a certain extent. In addition, the introduction of the Si negative electrode can also greatly reduce the cycle life of the battery, so that the lithium iron phosphate battery loses the characteristics of better cost advantage and cycle life. Therefore, the addition of silicon or silicon oxide as an active material with a high energy density to the negative electrode is not a completely positive-acting solution.
At present, in the field with higher energy density requirement, such as the field of power batteries, a certain application bottleneck still exists in the lithium battery taking lithium iron phosphate as a positive electrode.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a secondary battery, a preparation method thereof and an electric device, which aim to ensure that the secondary battery has high energy density and simultaneously has better cycle life.
The invention is realized in the following way:
in a first aspect, the present invention provides a battery comprising a positive electrode sheet, a negative electrode sheet, and a separator;
the positive pole piece comprises a positive current collector and a positive active coating coated on at least one side surface of the positive current collector; the positive electrode active coating comprises lithium iron phosphate;
the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating coated on at least one side surface of the negative electrode current collector; the negative electrode active coating comprises graphite;
performance parameter z=of secondary battery
Z is more than or equal to 9 and less than or equal to 13;
wherein V is E.D. Represents the volumetric energy density of the secondary battery in Wh/L;
D 90 indicating accumulated particles of lithium iron phosphateThe particle size corresponding to the degree distribution number reaching 90 percent is expressed as mu m;
C.W. represents the areal density of the positive electrode active coating layer on one side surface of the positive electrode current collector in mg/cm 2 ；
T 1 The thickness of the positive electrode current collector is expressed in μm;
T 2 the thickness of the negative electrode current collector is expressed in μm;
T 3 the thickness of the separator is expressed in μm.
In an alternative embodiment, the performance parameter Z satisfies: z is more than or equal to 10 and less than or equal to 12;
preferably, Z is more than or equal to 10.5 and less than or equal to 11.5;
more preferably, 10.76.ltoreq.Z.ltoreq.11.39.
In an alternative embodiment, the C.W. has a value in the range of 22mg/cm 2 ≤C.W.≤60mg/cm 2 ；
Preferably, the positive electrode active coating further includes a conductive agent, a binder, and a dispersing agent;
the mass ratio of the lithium iron phosphate in the positive electrode active coating is 92-99%.
In an alternative embodiment, the thickness T of the positive current collector 1 The value range of (2) is 6-20 mu m;
preferably, the positive electrode current collector is an aluminum foil, and the thickness of the aluminum foil is 6 μm-15 μm;
preferably, the positive electrode current collector includes a first substrate and a carbon layer, the first substrate is an aluminum foil, the carbon layer is positioned on the surface of the first substrate, and the thickness of the carbon layer is 0.2 μm-3 μm.
In an alternative embodiment, the thickness T of the negative electrode current collector 2 The range of the value of (2) is 4-12 mu m;
preferably, the negative electrode current collector is a copper foil or a composite copper foil;
preferably, the thickness of the negative electrode current collector is 4 μm to 10 μm.
In an alternative embodiment, V E.D. The range of the value of (C) is 420Wh/L-550Wh/L.
In an alternative embodiment, D 90 The range of the value of (C) is 5 μm-10 μm.
In the alternativeIn an embodiment, the thickness T of the isolation film 3 The range of the value of (2) is 5-26 mu m;
preferably, the release film comprises a second substrate and a modified coating attached to a surface of the second substrate; wherein the second substrate is at least one selected from polypropylene (PP) and Polyethylene (PE), and the modified coating comprises a ceramic material;
more preferably, the second substrate has a thickness of 5 μm to 20 μm and the modified coating has a thickness of 1 μm to 6 μm.
In a second aspect, the present invention provides a method for manufacturing a secondary battery, comprising: the secondary battery according to any one of the foregoing embodiments is produced under the parameter conditions such that the performance parameter Z of the secondary battery satisfies the value requirement.
In a third aspect, the present invention provides an electrical device comprising any one of the secondary batteries of the preceding embodiments.
The invention has the following beneficial effects: the volume energy density of the lithium iron phosphate battery, the D90 granularity of the lithium iron phosphate, the surface density of the positive electrode active coating and the thicknesses of the positive electrode current collector, the negative electrode current collector and the isolating film are limited to meet a specific relation, so that the volume energy density of the battery can be remarkably improved, and the battery can simultaneously have higher energy density and better cycle performance.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The embodiment of the invention provides a secondary battery, which comprises a positive electrode plate, a negative electrode plate and a separation film, wherein the separation film is used for preventing the positive electrode plate and the negative electrode plate from contacting to cause internal short circuit. The inventor meets a specific relation by limiting the relevant parameters of the positive pole piece, the negative pole piece and the isolating film, so that the secondary battery has high energy density and better cycle life.
Specifically, the positive electrode plate comprises a positive electrode current collector and a positive electrode active coating coated on at least one side surface of the positive electrode current collector; the positive electrode active coating comprises lithium iron phosphate; the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating coated on at least one side surface of the negative electrode current collector; the negative electrode active coating includes graphite. The specific relational expression provided by the embodiment of the invention aims at the situation that the positive electrode active material is lithium iron phosphate and the negative electrode active material is graphite.
Performance parameter z=of secondary battery
；
Wherein V is E.D. Represents the volumetric energy density of the secondary battery in Wh/L;
D 90 the particle size corresponding to the cumulative particle size distribution number of lithium iron phosphate reaching 90% is expressed in mu m;
C.W. represents the areal density of the positive electrode active coating on one side surface of the positive electrode current collector in mg/cm 2 ；
T 1 The thickness of the positive electrode current collector is expressed in μm;
T 2 the thickness of the negative electrode current collector is expressed in μm;
T 3 the thickness of the separator is expressed in μm.
The performance parameter Z of the secondary battery satisfies: z is more than or equal to 9 and less than or equal to 13, and can be specifically 9, 10, 11, 12, 13 and the like, or can be any value between the adjacent values. The value of Z is preferably within the above range, and the secondary battery can have a high energy density and a good cycle life.
In some embodiments, the performance parameter Z satisfies: z is more than or equal to 10 and less than or equal to 12; preferably, Z is more than or equal to 10.5 and less than or equal to 11.5; more preferably, 10.76.ltoreq.Z.ltoreq.11.39. By further preferably selecting the value of Z, the overall performance of the secondary battery can be further improved.
The following describes each parameter in the relational expression of the performance parameter Z of the secondary battery one by one:
. secondary batteryVolumetric energy density V of (2) E.D The value of (2) is 420Wh/L-550Wh/L, and the control is preferably carried out within the above range so as to ensure that the secondary battery has higher energy density.
D 90 Particle diameter D of lithium iron phosphate capable of reacting with positive electrode active material 90 The range of the value of (2) is 5 μm to 10. Mu.m, which is favorable for the secondary battery to obtain more ideal energy density and cycle performance. Specifically, D 90 The values of (2) may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.
The surface density of the positive electrode active coating on one side surface of the positive electrode current collector is calculated by a single-sided coating, and the value range of the C.W. is 22mg/cm 2 ≤C.W.≤60mg/cm 2 . The positive electrode active coating comprises a positive electrode active material, a conductive agent, a binder and a dispersing agent.
The mass ratio of the lithium iron phosphate in the positive electrode active coating is 92% -99%, such as 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% and the like. The positive electrode active material is generally considered to have a single-sided coating area density C.W. Positive electrode active material =A*C.W. Positive electrode active coating A is the ratio of the positive electrode active material in the positive electrode active coating, and the range of A is 92-99% and C.W. Positive electrode active coating ≥22mg/cm 2 。
Specifically, the positive electrode active material is mainly lithium iron phosphate (LiFePO 4 ) It is also possible to contain a small amount of doping elements such as Ti, al, mg, V, ni, mn, etc., the kind of doping element may be 1 or more, and the content of each doping element is within 5000 ppm.
Specifically, the conductive agent, the binder and the dispersing agent are conventional additives for preparing the positive electrode sheet, and the types and the amounts of the additives are not limited. For example, the conductive agent can be conductive carbon black, conductive graphene or conductive carbon nano tube, and the mass ratio of the conductive agent in the positive electrode active coating can be 0.2% -2%; for example, the binder can be polyvinylidene fluoride, polyimide, vinylidene fluoride-hexafluoropropylene copolymer and the like, and the mass ratio of the binder in the positive electrode active coating can be 0.5-2.5%; for example, the dispersing agent can be polyvinylpyrrolidone, polyethylene glycol, polyanion high molecular polymer, etc., and the mass ratio of the dispersing agent in the positive electrode active coating can be 0.1-0.5%.
Thickness T of positive electrode current collector 1 The range of the value of (C) is 6 μm-20 μm. Specifically T 1 The values of (2) may be 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.
In some embodiments, the positive electrode current collector may be an aluminum foil, but is not limited thereto. The thickness of the aluminum foil may be 6 μm to 15 μm, for example, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, etc.
In some embodiments, the positive electrode current collector includes a first substrate that is an aluminum foil and a carbon layer on a surface of the first substrate to improve conductive performance by forming the carbon layer, the carbon layer may have a thickness of 0.2 μm to 3 μm, such as 0.2 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, and the like.
Thickness T of negative electrode current collector 2 The range of the values is 4 μm to 12. Mu.m, for example, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, etc.
In some embodiments, the negative electrode current collector is a copper foil or a composite copper foil, which may be 4 μm to 10 μm thick, such as 4 μm, 6 μm, 8 μm, 10 μm, etc. The substrate of the negative electrode current collector is attached with a negative electrode active coating, the negative electrode active coating comprises a negative electrode active material, and the negative electrode active material can be a graphite material, and can be artificial graphite or natural graphite or a mixture of the artificial graphite and the natural graphite.
Similarly, the negative electrode active material has a single-sided coating area density C.W. Negative electrode active material =B*C.W. Negative electrode active coating B is the duty cycle of the negative electrode active material on the single-sided coating of the negative electrode current collector, C.W. Negative electrode active coating In the range of 8mg/cm 2 -15mg/cm 2 The range of B is 92% -99%.
In some embodiments, the negative active coating includes a negative active material, a conductive agent, a binder, and a dispersing agent, where the conductive agent, the binder, and the dispersing agent are conventional additives used in preparing a negative electrode sheet, and the types and the amounts thereof are not limited.
Thickness T of the isolation film 3 The value range is 5 μm to 26. Mu.m, for example, 5. Mu.m,10 μm, 15 μm, 20 μm, 25 μm, 26 μm, etc.
In some embodiments, the release film includes a second substrate and a modified coating attached to a surface of the second substrate. In other embodiments, the release film may also have only the second substrate, without the modified coating.
The second substrate is at least one selected from polypropylene (PP) and Polyethylene (PE), and the material may be PP, PE, or PP/PE composite substrate. The second substrate of the release film has a thickness of 5 μm to 20 μm, for example, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, etc.
The modified coating may be a ceramic material, and the thickness of the modified coating is generally 1 μm to 6 μm, for example, 1 μm, 3 μm, 4 μm, 6 μm, etc. Specifically, the material of the modified coating can be alumina or an adhesive, or an alumina/adhesive composite coating, and the adhesive can be polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol or styrene-butadiene rubber, etc.
The embodiment of the invention provides a preparation method of a secondary battery, which comprises the following steps: the preparation is performed according to the parameter conditions of the secondary battery in the above embodiment, and the performance parameter Z of the secondary battery is made to satisfy the value requirement, and other preparation processes may refer to the prior art except for controlling the value of the specific parameter.
The embodiment of the invention also provides an electric device which comprises the secondary battery, can also comprise other structures such as an electric appliance and the like, and is not limited in type.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
Example 1
The embodiment provides a method for manufacturing a secondary battery, which includes the steps of:
(1) Preparation of positive pole piece
Taking lithium iron phosphate as an anode active material, wherein the doping element is Ti, the content of the doping element is 400ppm, and the particle size corresponding to the accumulated particle size distribution number of the lithium iron phosphate anode reaching 90% meets the requirement.
The positive electrode active material lithium iron phosphate 955g, conductive agent (conductive carbon black) 20g, binder (polyvinylidene fluoride) 21g and dispersant (polyvinylpyrrolidone) 4g are mixed to form slurry, wherein the solvent is NMP, and the solid content is 58%. And uniformly coating the slurry on the A/B surface of the positive current collector, and obtaining the coated pole piece by a heating and drying mode. And compacting the pole piece by a rolling mode to obtain the positive pole piece.
(2) Preparation of negative pole piece
954g of negative electrode active material artificial graphite, 12g of conductive agent (conductive carbon black), 21g of binder (styrene-butadiene rubber) and 13g of dispersing agent (sodium carboxymethyl cellulose) are mixed to form slurry, wherein the solvent is deionized water, and the solid content is 55%. And uniformly coating the slurry on the A/B surface of the negative current collector, and obtaining the coated pole piece by a heating and drying mode. And compacting the pole piece by a rolling mode to obtain the negative pole piece.
(3) Preparation of a separation film
The PE base film was taken, 3g of alumina and 1g of polyvinylidene fluoride were mixed to form a slurry, and the slurry was applied to both sides of the PE base film and dried.
(4) Assembly
And forming a dry cell by winding or laminating the positive electrode plate, the negative electrode plate and the isolating film, packaging the dry cell in a soft package and a square aluminum shell, and obtaining a finished product cell through the procedures of liquid injection, formation, aging, capacity division, film coating and the like.
The present embodiment also provides a secondary battery, prepared by the above-described preparation method, V E.D. 、D 90 C.w. (single-sided coating surface density of positive electrode sheet), T 1 、T 2 、T 3 The values of the parameters of (2) are shown in Table 1.
Examples 2 to 7
Examples 2-7 differ from example 1 only in that: by controlling V E.D. 、D 90 C.w. (surface density of positive electrode sheet), T 1 、T 2 、T 3 The values of the final performance parameters Z are made different, as shown in table 1.
Comparative examples 1 to 2
Comparative examples 1-2 differ from example 1 only in that: by controlling V E.D. 、D 90 C.w. (surface density of positive electrode sheet), T 1 、T 2 、T 3 The values of the final performance parameters Z are made different, as shown in table 1.
Test example 1
The secondary batteries prepared in examples and comparative examples were tested for capacity retention using a conventional method, and the results are shown in table 1.
Table 1 examples and comparative examples parameters and performance test results of secondary batteries
As can be seen from Table 1, the energy density and cycle life are better balanced when Z is 10-12, so that the overall cell energy density is effectively improved (above 420 Wh/L) and the cycle is maintained at a better level. More preferably 10.5 to 11.5, most preferably 10.76 to 11.39.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The secondary battery is characterized by comprising a positive electrode plate, a negative electrode plate and a separation film;
the positive electrode plate comprises a positive electrode current collector and a positive electrode active coating coated on at least one side surface of the positive electrode current collector; the positive electrode active coating comprises lithium iron phosphate;
the negative electrode plate comprises a negative electrode current collector and a negative electrode active coating coated on at least one side surface of the negative electrode current collector; the negative electrode active coating comprises graphite;
performance parameter z=of the secondary battery
Z is more than or equal to 9 and less than or equal to 13;
wherein V is E.D. Represents the volumetric energy density of the secondary battery in Wh/L;
D 90 the particle size corresponding to the cumulative particle size distribution number of lithium iron phosphate reaching 90% is expressed in mu m;
C.W. represents the areal density of the positive electrode active coating on one side surface of the positive electrode current collector in mg/cm 2 ；
T 1 The thickness of the positive electrode current collector is expressed in μm;
T 2 the thickness of the negative electrode current collector is expressed in μm;
T 3 the thickness of the separator is expressed in μm.
2. The secondary battery according to claim 1, wherein the performance parameter Z satisfies: z is more than or equal to 10 and less than or equal to 12.
3. The secondary battery according to claim 1 or 2, wherein the value of c.w. is in the range of 22mg/cm 2 ≤C.W.≤60mg/cm 2 ；
The positive electrode active coating further comprises a conductive agent, a binder and a dispersing agent;
the mass ratio of the lithium iron phosphate in the positive electrode active coating is 92-99%.
4. The secondary battery according to claim 3, wherein the thickness T of the positive electrode current collector 1 The value range of (2) is 6-20 mu m;
the positive current collector is aluminum foil, and the thickness of the aluminum foil is 6-15 mu m;
or, the positive electrode current collector comprises a first substrate and a carbon layer, wherein the first substrate is aluminum foil, the carbon layer is positioned on the surface of the first substrate, and the thickness of the carbon layer is 0.2-3 mu m.
5. The secondary battery according to claim 1 or 2, wherein the negative electrode is a negative electrodeThickness T of polar current collector 2 The range of the value of (2) is 4-12 mu m;
the negative current collector is copper foil or composite copper foil.
6. The secondary battery according to claim 1 or 2, wherein V E.D. The range of the value of (C) is 420Wh/L-550Wh/L.
7. The secondary battery according to claim 1 or 2, wherein D 90 The range of the value of (C) is 5 μm-10 μm.
8. The secondary battery according to claim 1 or 2, wherein the thickness T of the separator film 3 The range of the value of (2) is 5-26 mu m;
the release film comprises a second substrate and a modified coating, wherein the modified coating is attached to the surface of the second substrate; wherein the second substrate is selected from at least one of polypropylene and polyethylene, and the modified coating comprises a ceramic material;
the thickness of the second substrate is 5-20 mu m, and the thickness of the modified coating is 1-6 mu m.
9. A method of manufacturing a secondary battery, comprising: the parameter condition of the secondary battery according to any one of claims 1 to 8 is prepared such that the performance parameter Z of the secondary battery satisfies the value requirement.
10. An electric device comprising the secondary battery according to any one of claims 1 to 8.
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