CN113594412A - Lithium battery positive plate with sandwich structure and lithium battery - Google Patents
Lithium battery positive plate with sandwich structure and lithium battery Download PDFInfo
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- CN113594412A CN113594412A CN202110914296.8A CN202110914296A CN113594412A CN 113594412 A CN113594412 A CN 113594412A CN 202110914296 A CN202110914296 A CN 202110914296A CN 113594412 A CN113594412 A CN 113594412A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 27
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical group [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims abstract description 72
- 239000011248 coating agent Substances 0.000 claims abstract description 44
- 238000000576 coating method Methods 0.000 claims abstract description 44
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical group [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 32
- 239000011230 binding agent Substances 0.000 claims abstract description 8
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 5
- 239000010410 layer Substances 0.000 claims description 47
- 239000002002 slurry Substances 0.000 claims description 32
- 239000007784 solid electrolyte Substances 0.000 claims description 20
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 14
- 239000002270 dispersing agent Substances 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 14
- 229910001416 lithium ion Inorganic materials 0.000 claims description 14
- 239000004576 sand Substances 0.000 claims description 13
- 239000006258 conductive agent Substances 0.000 claims description 11
- 239000002033 PVDF binder Substances 0.000 claims description 8
- 239000002041 carbon nanotube Substances 0.000 claims description 8
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 8
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 8
- 238000001354 calcination Methods 0.000 claims description 7
- 238000007709 nanocrystallization Methods 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 239000012298 atmosphere Substances 0.000 claims description 4
- 239000006229 carbon black Substances 0.000 claims description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 4
- 239000003792 electrolyte Substances 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910015944 LiMn0.8Fe0.2PO4 Inorganic materials 0.000 claims description 3
- 239000002202 Polyethylene glycol Substances 0.000 claims description 3
- CVJYOKLQNGVTIS-UHFFFAOYSA-K aluminum;lithium;titanium(4+);phosphate Chemical compound [Li+].[Al+3].[Ti+4].[O-]P([O-])([O-])=O CVJYOKLQNGVTIS-UHFFFAOYSA-K 0.000 claims description 3
- 239000013078 crystal Substances 0.000 claims description 3
- 238000003801 milling Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 229910016096 LiMn0.5Fe0.5PO4 Inorganic materials 0.000 claims description 2
- 229910015831 LiMn0.6Fe0.4PO4 Inorganic materials 0.000 claims description 2
- 229910015855 LiMn0.7Fe0.3PO4 Inorganic materials 0.000 claims description 2
- 229910016153 LiMn0.9Fe0.1PO4 Inorganic materials 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- NRJJZXGPUXHHTC-UHFFFAOYSA-N [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] Chemical compound [Li+].[O--].[O--].[O--].[O--].[Zr+4].[La+3] NRJJZXGPUXHHTC-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 229910000659 lithium lanthanum titanates (LLT) Inorganic materials 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 2
- 239000011247 coating layer Substances 0.000 claims 1
- 238000010276 construction Methods 0.000 claims 1
- 229910052782 aluminium Inorganic materials 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- 239000010405 anode material Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 239000010406 cathode material Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000005087 graphitization Methods 0.000 description 3
- 238000003837 high-temperature calcination Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229910015645 LiMn Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical compound [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 2
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 102000004310 Ion Channels Human genes 0.000 description 1
- 239000005279 LLTO - Lithium Lanthanum Titanium Oxide Substances 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- -1 lithium hexafluorophosphate Chemical group 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a sandwich-structured lithium battery positive plate, which comprises a positive current collector and a positive active layer, wherein the positive active layer comprises a conductive layer, a first active layer and a second active layer which are sequentially coated on the positive current collector, and the sandwich-structured lithium battery positive plate comprises: the conducting layer is a coating consisting of a conducting agent and a binder, the first active layer is a lithium manganate coating or a ternary material coating, and the second active layer is a lithium iron manganese phosphate coating. The lithium battery positive plate with the sandwich structure can improve the conductivity of lithium manganate and the safety performance of a battery.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium battery positive plate with a sandwich structure and a lithium ion battery.
Background
Spinel type lithium manganate (LiMn)2O4) The lithium ion battery anode material is an anode material with a three-dimensional lithium ion channel and has the advantages of rich resources, low cost, high voltage, good low-temperature performance and the like. However, during the charging and discharging processes, trivalent Mn in the material is easy to disproportionate to generate soluble divalent Mn, so that the structure is changed. Particularly, at high temperature, hydrofluoric acid generated by decomposition of lithium hexafluorophosphate in the electrolyte plays a role in catalysis, and the structural change of lithium manganate is accelerated, so that the high-temperature performance of lithium manganate is poor. The lithium iron manganese phosphate material has a stable olivine structure, does not change in the structure in the lithium ion de-intercalation process, and has good high-temperature cycle performance and safety. However, the lithium manganese iron phosphate has the disadvantages of low electronic conductivity, low lithium ion diffusion coefficient, two voltage platforms (4.1V and 3.4V) and the like, and thus the large-scale application of the lithium manganese iron phosphate is limited.
Because spinel-type lithium manganate and lithium manganese iron phosphate both have inherent defects as cathode materials, in practical application, in order to overcome the defects of spinel-type lithium manganate and lithium manganese iron phosphate, the spinel-type lithium manganate and the lithium manganese iron phosphate are generally used in a matched manner, for example, by adopting mixing at different ratios, layered coating or cladding. For example, chinese patent publication No. CN201811599210.1 discloses a positive electrode for a lithium ion battery, in which two lithium manganese iron phosphate materials are used as positive active materials, so that on one hand, the good safety and cycle performance of the lithium manganese iron phosphate material can be utilized, and on the other hand, the high energy density and good processability of the lithium manganese iron phosphate material can be utilized, and the prepared battery has high volume energy density, good cycle performance, excellent safety and good processability.
However, there are some defects when lithium manganate is used as a positive electrode material: because the conductivity of lithium manganate is poor, the lithium manganate can affect the transmission performance of electrons when used as a positive electrode material. In addition, the high-temperature performance of lithium manganate is poor, and the safety performance of the lithium battery can be affected.
Disclosure of Invention
The invention aims to provide a lithium battery positive plate with a sandwich structure, which can improve the conductivity of lithium manganate and the safety performance of a battery.
In order to solve the technical problems, the invention provides the following technical scheme:
the invention provides a sandwich-structured lithium battery positive plate which comprises a positive current collector and a positive active layer, wherein the positive active layer comprises a conductive layer, a first active layer and a second active layer which are sequentially coated on the positive current collector. Wherein:
the conducting layer is a coating consisting of a conducting agent and a binder, the first active layer is a lithium manganate coating or a ternary material coating, and the second active layer is a lithium iron manganese phosphate coating.
Furthermore, the thickness of the conducting layer is 1-5 μm, the thickness of the first active layer is 20-150 μm, and the thickness of the second active layer is 30-180 μm. The total thickness of the rolled pole piece is 171 +/-5 mu m.
Furthermore, in the conducting layer, the ratio of the conducting agent to the binder is 1: 1-3.
Further, the conductive agent is selected from one or more of carbon black conductive agent, graphite conductive agent and carbon nano tubes, and the binder is polyvinylidene fluoride.
Further, in the lithium manganate coating, the adopted lithium manganate is capacity type lithium manganate D509 to 18 μm; or the adopted lithium manganate is single-crystal lithium manganate D506-12 μm;
in the ternary material coating, the adopted ternary material is one or two of NCM811 and NCM523, and D of the ternary material508 to 12 μm.
Further, in the lithium iron manganese phosphate coating, the lithium iron manganese phosphate is adopted as modified lithium iron manganese phosphate, and the preparation method of the modified lithium iron manganese phosphate comprises the following steps:
a. carrying out nanocrystallization on the micron-sized lithium manganese iron phosphate and a dispersing agent to obtain a nanoscale lithium manganese iron phosphate slurry; carrying out nanocrystallization on the micron-sized solid electrolyte to obtain nanoscale solid electrolyte slurry;
b. drying the lithium iron manganese phosphate slurry obtained in the step a and the solid electrolyte slurry, and then uniformly mixing to obtain a composite material;
c. calcining the composite material obtained in the step b in an inert atmosphere to obtain modified lithium manganese iron phosphate;
the dispersing agent is one or more of polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol, and the addition amount of the dispersing agent is 1-5 wt% of the lithium manganese iron phosphate; in the modified lithium manganese iron phosphate, the content of the solid electrolyte is 0.3 wt% -3 wt%.
According to the invention, the micro-scale lithium manganese iron phosphate is subjected to sanding and nanocrystallization treatment and then is mixed with the solid electrolyte to prepare the slurry, and the nano-scale lithium manganese iron phosphate particles enable a lithium ion deintercalation path to be shorter and an ion diffusion coefficient to be higher.
Further, in the step a, the lithium iron manganese phosphate is LiMn0.5Fe0.5PO4、LiMn0.6Fe0.4PO4、LiMn0.7Fe0.3PO4、LiMn0.8Fe0.2PO4、LiMn0.9Fe0.1PO4One of them, D50Preferably 1 to 10 μm.
Further, in step a, the solid electrolyte may be selected from solid electrolytes commonly used in the art, including but not limited to one or more of Lithium Aluminum Titanium Phosphate (LATP), Lithium Lanthanum Titanate (LLTO), Lithium Lanthanum Zirconium Oxide (LLZO). Preferably, D of the solid electrolyte505 to 100 μm.
Further, in the step a, a sand mill is adopted for nanocrystallization, the diameter of a zirconia ball used in sand milling is 0.3mm, the mass ratio of the zirconia ball to the materials to water is 10:1, the rotating speed of the sand mill is 2000r/min, and the grinding time is 30-120 min;
further, in the step b, the drying temperature is 100-150 ℃, and the drying time is 30 min-2 h;
further, in the step c, the inert atmosphere is nitrogen or argon, the calcining temperature is 800-1000 ℃, and the calcining time is 4-10 hours. The composite material is calcined at a high temperature of 800-1000 ℃, and the graphitization degree of the dispersing agent is mainly improved. The higher the carbonization temperature of the dispersing agent is, the higher the graphitization degree of the dispersing agent is, and the higher the graphitization degree is, the conductivity of the material can be improved, and in addition, the resistance of the grain boundary of the solid electrolyte during high-temperature calcination is smaller, so that the high-temperature calcination is beneficial to improving the ionic conductivity of the cathode material.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate, electrolyte and a diaphragm, wherein the positive plate is the lithium battery positive plate with the sandwich structure.
Compared with the prior art, the invention has the beneficial effects that:
1. because the conductivity of lithium manganate is poor, the lithium manganate can affect the transmission performance of electrons when used as a positive electrode material. In order to solve the problem, the invention constructs the positive plate with the sandwich structure, wherein the conducting layer consisting of the conducting agent and the binder is arranged close to the positive current collector, the outermost layer is the lithium manganese iron phosphate coating, and the lithium manganate is arranged between the conducting layer and the lithium manganese iron phosphate coating. In addition, after the battery is assembled by the positive plate lamination, the lithium manganese iron phosphate coating is arranged on the outermost side of the positive plate, so that the lithium manganese iron phosphate has good high-temperature performance, and the battery has high safety.
2. The cathode material contains modified lithium manganese iron phosphate, the modified lithium manganese iron phosphate is obtained by preparing slurry by nanocrystallizing a solid electrolyte, lithium manganese iron phosphate and a dispersing agent and calcining at high temperature, wherein the lithium manganese iron phosphate with a nanostructure has high electronic conductivity, small internal resistance and high ionic conductivity of the nano solid electrolyte, and the polarization and manganese dissolution of the lithium manganese iron phosphate are reduced by the combined use of the two, so that the cycle performance is improved; the dispersing agent is used, so that the lithium manganese iron phosphate and the solid electrolyte can be well and uniformly mixed, and the cycle performance of the material can be improved; and through high-temperature calcination, the dispersing agent is carbonized into a carbon material coated on the surface of the lithium manganese iron phosphate, so that the electronic conductivity of the lithium manganese iron phosphate material is improved on one hand, the contact between active substances is further improved on the other hand, the side reaction between the active substances and electrolyte is reduced, and the cycle and rate capability of the material are improved.
3. According to the invention, the modified lithium manganese iron phosphate and the lithium manganese oxide are used in a composite manner, so that a high-speed ion-electron double transmission channel can be established, the polarization and manganese dissolution of the lithium manganese oxide can be reduced, and the cycle performance of the battery is improved.
Drawings
FIG. 1 is a schematic structural diagram of a positive plate with a sandwich structure according to the present invention;
fig. 2 is a graph comparing the high temperature cycle life of square aluminum cell prepared in example 2 and comparative example 1;
fig. 3 is a graph comparing the high temperature cycle life of square aluminum cell prepared in example 2 and comparative example 2;
wherein: s1, a positive current collector; s2, a conductive layer; s3, a first active layer; s4, a second active layer.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The experimental methods used in the following examples are conventional methods unless otherwise specified, and materials, reagents and the like used therein are commercially available without otherwise specified.
Example 1: preparation of modified lithium manganese iron phosphate
(1) Adding 1kg of lithium manganese iron phosphate, 30g of polyethylene glycol and 1.4kg of deionized water into a sand mill for sanding, wherein the lithium manganese iron phosphate is LiMn0.8Fe0.2PO4The grain diameter is 2.5 mu m, the diameter of zirconia balls in the sand mill is 0.3mm, the mass ratio of the zirconia balls to the materials is 10:1, and the rotating speed of the sand mill is 2000 r/min. Grinding for 30min to obtain nanoscale lithium iron manganese phosphate slurry, and testing the particle size D of the slurry50Is 200 nm. And then drying the lithium iron manganese phosphate slurry in a vacuum box at the drying temperature of 100 ℃ for 1h to obtain the nano lithium iron manganese phosphate (containing the dispersing agent).
(2) 1kg of Lithium Aluminum Titanium Phosphate (LATP) and 1.4kg of deionized water are added into a sand mill for sand milling, wherein the particle size of the LATP is 50 mu m, the diameter of a zirconia ball in the sand mill is 0.3mm, the mass ratio of the zirconia ball to materials is 10:1, and the rotating speed of the sand mill is 2000 r/min. Grinding for 30min to obtain nanoscale solid electrolyte slurry, and testing particle size D50Is 500 nm. And then drying the solid electrolyte slurry in a vacuum box at the drying temperature of 120 ℃ for 1h to obtain the nano LATP.
(3) Sintering 500g of nano lithium manganese iron phosphate (containing a dispersing agent) and 5g of nano LATP at 800 ℃ for 5 hours in a nitrogen atmosphere, wherein the heating rate is 5 ℃/min, and cooling along with a furnace to obtain a modified lithium manganese iron phosphate anode material D50Is 1 μm.
Example 2: preparation sandwich structure's lithium cell positive plate
As shown in fig. 1, the present embodiment provides a positive plate of a lithium battery with a sandwich structure, including a positive current collector S1 and a positive active layer, where the positive active layer includes a conductive layer S2, a first active layer S3 and a second active layer S4 sequentially coated on the positive current collector S1; the first active layer S3 is a lithium manganate coating, and the second active layer S4 is a modified lithium iron manganese phosphate coating. The preparation method of the conducting layer S2, the lithium manganate coating and the modified lithium iron manganese phosphate coating comprises the following steps:
(1) 0.1kg of carbon black conductive agent, 0.1kg of carbon nanotube conductive agent and 0.4kg of PVDF are mixed to prepare slurry, the slurry is coated on an aluminum foil with the thickness of 15 mu m and dried, and the conductive layer with the thickness of 2 mu m is obtained after rolling.
(2) 5kg of spinel-type lithium manganate, 0.05kg of sp, 0.05kg of CNTs and 0.2kg of PVDF were added to 10L planetary mixer. Wherein the lithium manganate is single-crystal lithium manganate D50Is 10 μm. Stirring for 3-5 h, adding N-methyl pyrrolidone in the stirring process to adjust the viscosity to obtain uniform lithium manganate slurry, and controlling the viscosity of the slurry to be 10000-12000 mpa.s. Coating the obtained lithium manganate slurry on a conductive layer and drying, wherein the coating surface density is 200g/m2And tabletting by using a roller press to obtain the lithium manganate coating with the thickness of 120 mu m.
(3) Adding 5kg of modified lithium manganese iron phosphate prepared in example 1, 0.05kg of sp, 0.05kg of CNTs and 0.2kg of PVDF into a 10L planetary mixer, stirring for 3-5 h, adding N-methyl pyrrolidone during stirring to adjust viscosity, obtaining uniform lithium manganese iron phosphate slurry, and controlling the viscosity of the slurry to be 10000-12000 mpa.s. Coating the lithium iron manganese phosphate slurry on the surface of a lithium manganate coating and drying the lithium iron manganese phosphate slurry, wherein the coating surface density is 200g/m2And tabletting by using a roller press to obtain the modified lithium iron manganese phosphate coating with the thickness of 50 mu m.
The material is used as a positive plate to assemble a square aluminum shell lithium ion battery, the thickness of the battery is 21mm, the width of the battery is 115mm, the height of the battery is 108mm, the designed capacity is 23Ah, 18.34Ah of capacity remains after the battery is cycled for 600 times at 45 ℃, and the capacity retention rate is 79.7%.
Example 3: preparation sandwich structure's lithium cell positive plate
The embodiment provides a lithium battery positive plate with a sandwich structure, which comprises a positive current collector and a positive active layer, wherein the positive active layer comprises a conductive layer, a ternary material coating and a modified lithium iron manganese phosphate coating which are sequentially coated on the positive current collector, and the preparation method comprises the following steps:
(1) 0.1kg of carbon black conductive agent, 0.1kg of carbon nanotube conductive agent and 0.4kg of PVDF are mixed to prepare slurry, the slurry is coated on an aluminum foil with the thickness of 15 mu m and dried, and the conductive layer with the thickness of 2 mu m is obtained after rolling.
(2) 2.5kg of ternary NCM811, 2.5kg of ternary NCM523, 0.05kg of sp, 0.05kg of CNTs and 0.2kg of PVDF were introduced into a 10L planetary mixer. Wherein D of NCM811 and NCM52350Is 10 μm. Stirring for 3-5 h, and adding N-methyl pyrrolidone to adjust viscosity in the stirring processAnd obtaining uniform ternary material slurry, and controlling the viscosity of the slurry to be 10000-12000 mpa.s. Coating the obtained ternary material slurry on a conductive layer and drying, wherein the coating surface density is 200g/m2And tabletting by using a roller press to obtain the ternary material coating with the thickness of 100 mu m.
(3) Adding 5kg of modified lithium manganese iron phosphate prepared in example 1, 0.05kg of sp, 0.05kg of CNTs and 0.2kg of PVDF into a 10L planetary mixer, stirring for 3-5 h, adding N-methyl pyrrolidone during stirring to adjust viscosity, obtaining uniform lithium manganese iron phosphate slurry, and controlling the viscosity of the slurry to be 10000-12000 mpa.s. Coating the lithium iron manganese phosphate slurry on the surface of a ternary material coating and drying, wherein the coating surface density is 200g/m2And tabletting by using a roller press to obtain the modified lithium iron manganese phosphate coating with the thickness of 60 mu m.
The material is used as a positive plate to assemble a square aluminum shell lithium ion battery, the thickness of the battery is 21mm, the width of the battery is 115mm, the height of the battery is 108mm, the designed capacity is 23.2Ah, the 19.8Ah capacity of the battery is remained after the battery is cycled for 600 times at 45 ℃, and the capacity retention rate is 85.5%.
Comparative example 1
Comparative example 1 differs from example 2 in that: the positive electrode sheet of comparative example 1 had no conductive layer.
The material is used as a positive plate to assemble a square aluminum shell lithium ion battery, the thickness of the battery is 21mm, the width of the battery is 115mm, the height of the battery is 108mm, the designed capacity is 23Ah, the battery has 16.8Ah of capacity remained after 500 cycles at 45 ℃, and the capacity retention rate is 73.0%.
Comparative example 2
Comparative example 2 differs from example 2 in that: unmodified lithium manganese iron phosphate LiMn is used in the lithium manganese iron phosphate coating0.8Fe0.2PO4The particle size was 2.5. mu.m.
The material is used as a positive plate to assemble a square aluminum shell lithium ion battery, the thickness of the battery is 21mm, the width of the battery is 115mm, the height of the battery is 108mm, the designed capacity is 23Ah, 16.1Ah of capacity remains after the battery is cycled for 450 times at 45 ℃, and the capacity retention rate is 70.0%.
The results show that the lithium battery positive plate with the sandwich structure improves the cycle performance of the battery by arranging the conductive layer between the lithium manganate coating and the positive current collector and adopting the modified lithium manganese iron phosphate.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. The utility model provides a sandwich structure's lithium cell positive plate, includes anodal mass flow body and anodal active layer, its characterized in that, anodal active layer is including coating conducting layer, first active layer and the second active layer on the anodal mass flow body in proper order, wherein:
the conducting layer is a coating consisting of a conducting agent and a binder, the first active layer is a lithium manganate coating or a ternary material coating, and the second active layer is a lithium iron manganese phosphate coating.
2. The positive plate of the lithium battery with the sandwich structure as claimed in claim 1, wherein the conductive layer has a thickness of 1 to 5 μm, the first active layer has a thickness of 20 to 150 μm, and the second active layer has a thickness of 30 to 180 μm; the total thickness of the rolled pole piece is 171 +/-5 mu m.
3. The positive plate of the lithium battery with the sandwich structure as claimed in claim 2, wherein the ratio of the conductive agent to the binder in the conductive layer is 1: 1-3.
4. The positive electrode plate of the lithium battery with the sandwich structure as claimed in claim 1, wherein the conductive agent is one or more selected from carbon black conductive agent, graphite conductive agent and carbon nanotube, and the binder is polyvinylidene fluoride.
5. The sandwich-structured lithium battery positive plate as claimed in claim 1, wherein the lithium manganate coating layer is formed byThe lithium manganate is capacity type lithium manganate D509 to 18 μm; or the adopted lithium manganate is single-crystal lithium manganate D506-12 μm;
in the ternary material coating, the adopted ternary material is one or two of NCM811 and NCM523, and D of the ternary material508 to 12 μm.
6. The lithium battery positive plate with the sandwich structure according to claim 1, wherein lithium manganese iron phosphate adopted in the lithium manganese iron phosphate coating is modified lithium manganese iron phosphate, and the preparation method of the modified lithium manganese iron phosphate comprises the following steps:
a. carrying out nanocrystallization on the micron-sized lithium manganese iron phosphate and a dispersing agent to obtain a nanoscale lithium manganese iron phosphate slurry; carrying out nanocrystallization on the micron-sized solid electrolyte to obtain nanoscale solid electrolyte slurry;
b. drying the lithium iron manganese phosphate slurry obtained in the step a and the solid electrolyte slurry, and then uniformly mixing to obtain a composite material;
c. calcining the composite material obtained in the step b in an inert atmosphere to obtain modified lithium manganese iron phosphate;
the dispersing agent is one or more of polyvinylpyrrolidone, polyethylene glycol and polyvinyl alcohol, and the addition amount of the dispersing agent is 1-5 wt% of the lithium manganese iron phosphate; in the modified lithium manganese iron phosphate, the content of the solid electrolyte is 0.3 wt% -3 wt%.
7. The positive plate of lithium battery with sandwich structure as claimed in claim 6, wherein in step a, the lithium iron manganese phosphate is LiMn0.5Fe0.5PO4、LiMn0.6Fe0.4PO4、LiMn0.7Fe0.3PO4、LiMn0.8Fe0.2PO4、LiMn0.9Fe0.1PO4One of them, D501 to 10 μm.
8. A sandwich construction according to claim 6The lithium battery positive plate is characterized in that in the step a, the solid electrolyte is one of lithium aluminum titanium phosphate, lithium lanthanum titanate and lithium lanthanum zirconium oxide, and D is the solid electrolyte505 to 100 μm.
9. The positive electrode sheet of a lithium battery with a sandwich structure according to claim 6,
in the step a, a sand mill is adopted for nanocrystallization, the diameter of a zirconia ball used in sand milling is 0.3mm, the mass ratio of the zirconia ball to materials to water is 10:1, the rotating speed of the sand mill is 2000r/min, and the grinding time is 30-120 min;
in the step b, the drying temperature is 100-150 ℃, and the drying time is 30 min-2 h;
in the step c, the inert atmosphere is nitrogen or argon, the calcining temperature is 800-1000 ℃, and the calcining time is 4-10 hours.
10. A lithium ion battery comprises a positive plate, a negative plate, electrolyte and a diaphragm, and is characterized in that the positive plate is the positive plate of the lithium battery with a sandwich structure as claimed in any one of claims 1 to 9.
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