CN116544353B - Positive electrode plate, preparation method thereof and battery - Google Patents
Positive electrode plate, preparation method thereof and battery Download PDFInfo
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- CN116544353B CN116544353B CN202310828973.3A CN202310828973A CN116544353B CN 116544353 B CN116544353 B CN 116544353B CN 202310828973 A CN202310828973 A CN 202310828973A CN 116544353 B CN116544353 B CN 116544353B
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- 238000002360 preparation method Methods 0.000 title abstract description 6
- 239000011248 coating agent Substances 0.000 claims abstract description 80
- 238000000576 coating method Methods 0.000 claims abstract description 80
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 68
- 239000000463 material Substances 0.000 claims abstract description 62
- 238000000034 method Methods 0.000 claims abstract description 24
- 230000008569 process Effects 0.000 claims abstract description 18
- 239000013543 active substance Substances 0.000 claims abstract description 12
- 239000012299 nitrogen atmosphere Substances 0.000 claims abstract description 5
- 230000000630 rising effect Effects 0.000 claims abstract description 5
- 230000020169 heat generation Effects 0.000 claims description 67
- 239000011247 coating layer Substances 0.000 claims description 32
- 238000000498 ball milling Methods 0.000 claims description 27
- 239000000203 mixture Substances 0.000 claims description 21
- 239000011230 binding agent Substances 0.000 claims description 19
- 239000006258 conductive agent Substances 0.000 claims description 19
- 239000007774 positive electrode material Substances 0.000 claims description 18
- 239000003792 electrolyte Substances 0.000 claims description 17
- 239000007789 gas Substances 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- 229910052785 arsenic Inorganic materials 0.000 claims description 11
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 claims description 11
- 239000002243 precursor Substances 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
- 230000001681 protective effect Effects 0.000 claims description 9
- 239000002033 PVDF binder Substances 0.000 claims description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 8
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 8
- 239000000843 powder Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 7
- 238000012216 screening Methods 0.000 claims description 6
- 239000006230 acetylene black Substances 0.000 claims description 3
- 239000002041 carbon nanotube Substances 0.000 claims description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 3
- 229910021389 graphene Inorganic materials 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 44
- 229910052757 nitrogen Inorganic materials 0.000 description 23
- 239000007772 electrode material Substances 0.000 description 19
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 18
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 18
- 239000000460 chlorine Substances 0.000 description 17
- 229910052801 chlorine Inorganic materials 0.000 description 17
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 16
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 15
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 15
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 15
- 229910052710 silicon Inorganic materials 0.000 description 14
- 239000010703 silicon Substances 0.000 description 14
- 239000002270 dispersing agent Substances 0.000 description 12
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 10
- ZVLDJSZFKQJMKD-UHFFFAOYSA-N [Li].[Si] Chemical compound [Li].[Si] ZVLDJSZFKQJMKD-UHFFFAOYSA-N 0.000 description 9
- 229910000733 Li alloy Inorganic materials 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
- 239000001989 lithium alloy Substances 0.000 description 8
- 229910052698 phosphorus Inorganic materials 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 7
- 125000004430 oxygen atom Chemical group O* 0.000 description 7
- 239000002002 slurry Substances 0.000 description 7
- VKJKOXNPYVUXNC-UHFFFAOYSA-K trilithium;trioxido(oxo)-$l^{5}-arsane Chemical compound [Li+].[Li+].[Li+].[O-][As]([O-])([O-])=O VKJKOXNPYVUXNC-UHFFFAOYSA-K 0.000 description 7
- 239000013078 crystal Substances 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000006183 anode active material Substances 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 239000011888 foil Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 125000004437 phosphorous atom Chemical group 0.000 description 5
- -1 polypropylene Polymers 0.000 description 5
- 229920001155 polypropylene Polymers 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 238000001291 vacuum drying Methods 0.000 description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 4
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 239000011812 mixed powder Substances 0.000 description 4
- 239000011574 phosphorus Substances 0.000 description 4
- 229910052711 selenium Inorganic materials 0.000 description 4
- 239000011669 selenium Substances 0.000 description 4
- 238000001035 drying Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
- 238000005979 thermal decomposition reaction Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 230000032798 delamination Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- FKQOMXQAEKRXDM-UHFFFAOYSA-N [Li].[As] Chemical compound [Li].[As] FKQOMXQAEKRXDM-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229940000489 arsenate Drugs 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- PAZHGORSDKKUPI-UHFFFAOYSA-N lithium metasilicate Chemical compound [Li+].[Li+].[O-][Si]([O-])=O PAZHGORSDKKUPI-UHFFFAOYSA-N 0.000 description 1
- 229910052912 lithium silicate Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000005303 weighing 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
- 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
- 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
- H01M10/60—Heating or cooling; Temperature control
- H01M10/65—Means for temperature control structurally associated with the cells
- H01M10/654—Means for temperature control structurally associated with the cells located inside the innermost case of the cells, e.g. mandrels, electrodes or electrolytes
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, 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
- 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 provides a positive pole piece, a preparation method thereof and a battery, wherein the positive pole piece comprises a current collector and a positive active coating, and the positive active coating is arranged on the current collector; the positive electrode active coating comprises a positive electrode active substance, the positive electrode active substance is a lithium iron phosphate material containing doping elements, the doping elements are selected from DSC heat release of the positive electrode active coating in nitrogen atmosphere at a temperature rising speed of 5K/min in a temperature rising process of 30-400 ℃ under the condition that the mass percentage content M of the doping elements in the positive electrode active coating is 0.001-8%.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a positive pole piece, a preparation method thereof and a battery.
Background
Lithium ion batteries are one of the most widely used secondary batteries commercially at present, and have been widely used in mobile phones, electric vehicles and energy storage power stations. With the wide application of lithium ion batteries, the safety of the lithium ion batteries is also increasingly important. Lithium ion batteries typically include lithium-containing electrode materials and organic electrolytes that instantaneously generate significant amounts of heat when shorted or exposed to air. In particular, during actual operation, a plurality of cells are typically combined to form a module or container. This makes lithium ion batteries susceptible to thermal runaway problems.
Disclosure of Invention
Based on this, it is necessary to provide a positive electrode sheet to reduce the amount of heat generated by the positive electrode sheet and improve the safety of the battery as a whole.
According to some embodiments of the present disclosure, there is provided a positive electrode tab comprising a current collector and a positive electrode active coating disposed on the current collector;
the positive electrode active coating comprises a positive electrode active material, wherein the positive electrode active material is a lithium iron phosphate material containing doping elements, and the doping elements are selected from nonmetallic elements;
under the condition that the mass content M of the doping element in the positive electrode active coating is 0.001% -8%, the heat generation amount W of the positive electrode active coating per unit mass is less than or equal to 249J/g, and the heat generation amount W is DSC heat release amount of the positive electrode active coating per unit mass in the heating process of the positive electrode active coating in the nitrogen atmosphere at the heating speed of 5K/min within the range of 30-400 ℃.
In some embodiments of the present disclosure, the mass content M of the doping element in the positive electrode active coating layer is 0.05% -4%.
In some embodiments of the present disclosure, the mass content M of the doping element in the positive electrode active coating layer is 0.5% -1%.
In some embodiments of the present disclosure, the mass content of the doping element is controlled so that the heat generation amount W of the positive electrode active coating per unit mass is equal to or less than 208J/g.
In some embodiments of the present disclosure, the mass content of the doping element is controlled so that the heat generation amount W of the positive electrode active coating per unit mass is less than or equal to 169J/g.
In some embodiments of the present disclosure, the doping element is selected from nitrogen element, silicon element, chlorine element, arsenic element, or selenium element.
In some embodiments of the present disclosure, the mass content of the positive electrode active material in the positive electrode active coating layer is 90% or more.
In some embodiments of the present disclosure, the positive electrode active coating further includes a binder and a conductive agent, and the total mass content of the binder and the conductive agent in the positive electrode active coating is 2% -10%.
According to some embodiments of the present disclosure, there is also provided a method of preparing the positive electrode sheet as in the above embodiments, comprising the steps of:
mixing lithium iron phosphate and a precursor containing the doping elements according to a preset proportion, and performing ball milling treatment on the mixture obtained after mixing in a protective gas environment;
roasting the mixture subjected to ball milling treatment at a temperature of below 200 ℃ to form the positive electrode active material;
the positive electrode active coating layer including the positive electrode active material is prepared on the current collector.
Further, the present disclosure also provides a battery, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is disposed opposite to the negative electrode, the electrolyte is disposed between the positive electrode and the negative electrode, and the positive electrode is the positive electrode sheet according to any one of the above embodiments.
The lithium iron phosphate material containing doping elements is used as a positive electrode active material in the positive electrode sheet, the doping elements are selected from nonmetallic elements, and phosphorus atom sites or oxygen atom sites in a lithium iron phosphate crystal lattice are replaced by the doping elements. The proper content of nonmetallic elements can increase the lattice volume of lithium iron phosphate, enhance the interaction between phosphorus and oxygen atoms, and is beneficial to improving the structural stability in the intercalation and delamination process of lithium atoms. In addition, the nonmetallic elements embedded in the crystal lattice are beneficial to reducing the band gap, increasing the concentration of electrons and holes and improving the structural stability of the lithium iron phosphate material.
According to experimental verification, for the lithium iron phosphate material containing the doping element, under the condition that the mass content M of the doping element in the positive electrode active coating is 0.001% -8%, the heat generation amount W of the positive electrode active coating can be reduced, and the heat generation amount W of the positive electrode active coating with unit mass is less than or equal to 249J/g by controlling the mass content M of the doping element, wherein the heat generation amount W is obviously lower than the heat generation amount of the positive electrode active coating without the doping element. Compared with the positive electrode active coating without doping elements, the positive electrode active coating in the positive electrode plate has lower heat generation amount, so that the heat generation amount of the plate is effectively reduced from the source, and the overall safety of the battery can be improved.
Detailed Description
The present invention will be described more fully hereinafter in order to facilitate an understanding of the present invention. Preferred embodiments of this invention are presented herein. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
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 herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items. As used herein, "multiple" includes two and more items. As used herein, "above a certain number" should be understood to mean a certain number and a range of numbers greater than a certain number.
The present disclosure has been made by study to find that a lithium iron phosphate electrode material itself is decomposed at about 200 c during actual use, resulting in more heat generation thereof, which may cause further temperature rise of the battery, and increase the probability of thermal runaway of interlocking between the plurality of batteries of the battery module.
The disclosure provides a positive electrode plate, which comprises a current collector and a positive electrode active coating, wherein the positive electrode active coating is arranged on the current collector, the positive electrode active coating comprises a positive electrode active substance, the positive electrode active substance is a lithium iron phosphate material containing doping elements, and the doping elements are selected from nonmetallic elements. Under the condition that the mass content M of the doping element in the positive electrode active coating is 0.001% -8%, the heat generation amount W of the positive electrode active coating per unit mass is less than or equal to 249J/g, and the heat generation amount W is the DSC heat release amount of the positive electrode active coating per unit mass in the heating process of the positive electrode active coating in the nitrogen atmosphere at the heating rate of 5K/min within the range of 30-400 ℃.
According to experiments, the lithium iron phosphate material containing the doping element can reduce the heat generation amount W of the positive electrode active coating under the condition that the mass content M of the doping element in the positive electrode active material is 0.001% -8%, and the heat generation amount W of the positive electrode active coating with unit mass is less than or equal to 249J/g by controlling the mass content M of the doping element, wherein the heat generation amount W is obviously lower than that of the positive electrode active coating without the doping element. Compared with the positive electrode active coating without doping elements, the positive electrode active coating in the positive electrode plate has lower heat generation amount, so that the heat generation amount of the plate is effectively reduced from the source, and the overall safety of the battery can be improved.
It is understood that lithium iron phosphate, after being heated to a certain temperature, causes further heat generation of the positive electrode active coating itself, which is mainly derived from decomposition reaction of lithium iron phosphate, and is usually secondary heat generation occurring after the battery is heated, which is also one of main heat generation sources of the battery during thermal runaway. The heat generation amount W in the present disclosure refers to the heat release amount of the positive electrode active coating during DSC test. In particular, the gas conditions of the DSC test process can be set to be nitrogen atmosphere, the temperature rising rate can be set to be 5K/min, and the test temperature range can be set to be 30-400 ℃ so as to obtain the heat generation quantity as accurate as possible.
In some examples of this embodiment, the doping element is intercalated into the crystal lattice of the lithium iron phosphate and may be located at a phosphorus atom site or an oxygen atom site therein. The proper content of nonmetallic elements can increase the lattice volume of lithium iron phosphate, enhance the interaction between phosphorus and oxygen atoms, and is beneficial to improving the structural stability in the intercalation and delamination process of lithium atoms. In addition, the nonmetallic elements embedded in the crystal lattice are beneficial to reducing the band gap, increasing the concentration of electrons and holes and improving the structural stability of the lithium iron phosphate material. This allows the free energy of the lithium iron phosphate material to be reduced, thereby reducing its heat generation.
It is understood that determining whether a doping element is intercalated into the crystal lattice of lithium iron phosphate may be performed by determining the amount of the doping element and the total material of each element in the lithium iron phosphate. The ratio of phosphorus to oxygen is also relatively reduced when the doping element is embedded in the crystal lattice.
There are also some ways in the conventional art to improve safety, for example, coating a material such as inorganic salt on the surface of an electrode material as a protective layer to reduce the probability of short circuit of a battery at thermal runaway as much as possible and delay the short circuit process. However, these methods for improving safety often ignore heat release of the electrode material itself from the viewpoint of suppressing short-circuiting of the battery. The positive electrode plate is designed from the angle of the structure of the positive electrode active material, and the proper amount of doping elements are doped in the lithium iron phosphate to control the heat generation amount, so that the stability of an electrode material can be effectively improved, the heat generation amount of the electrode material in a thermal runaway process is reduced, the generation and aggregation of heat are radically reduced, and the safety performance of a battery is improved.
In the positive electrode active coating provided by the embodiment, the content of the doping element in the positive electrode active coating can be 0.001% -8%, and experiments prove that the heat generation amount of the positive electrode active coating can be obviously reduced when the nonmetallic element is in the doping content range.
In the positive electrode plate provided by the embodiment, the content of doping elements can be controlled so that the heat generation quantity W of the positive electrode active coating in unit mass is less than or equal to 249J/g. In contrast, the heat generation amount per unit mass of the positive electrode active coating layer containing no doping element is substantially 258J/g or more. Therefore, from the aspect of results, the heat generation amount W of the positive electrode active coating with unit mass is controlled to be less than or equal to 249J/g, so that the heat generation amount of the positive electrode plate can be effectively reduced, and the safety performance of the prepared battery is further improved.
In some examples of this embodiment, the heat generation amount W per unit mass of the positive electrode active coating is 92J/g to 249J/g. Further, the heat generation amount W of the positive electrode active coating layer per unit mass is 92J/g, 110J/g, 122J/g, 160J/g, 208J/g, 239J/g or 249J/g, and the heat generation amount W of the positive electrode active coating layer per unit mass may be in a range between any two of the above heat generation amounts.
It is understood that the mass content range of the doping element and the heat generation amount range per unit mass respectively define the positive electrode sheet of this embodiment from different angles, and generally, when the mass percentage content M of the doping element in the positive electrode active coating layer ranges from 0.001% to 8%, the heat generation amount W of the positive electrode active coating layer per unit mass can also be controlled below 249J/g.
In some examples of this embodiment, the mass content M of the doping element in the electrode active material may be 0.001%, 0.01%, 0.05%, 0.5%, 1%, 4% or 8%, of course, the mass content M of the doping element in the electrode active material may also be in a range between any two of the above.
Further, in some examples of this embodiment, the mass content M of the doping element in the electrode active material may be 0.05% -4%. The mass content M in this range can reduce the heat generation amount W of the positive electrode active coating more effectively.
In particular, in some examples of this embodiment, the mass content M of the doping element in the electrode active material may be 0.5% to 1%. The mass content M can greatly reduce the heat generation amount W of the positive electrode active coating within this range.
Further, in some examples of this embodiment, the heat generation amount W of the positive electrode active coating layer per unit mass is 208J/g or less during the temperature increasing treatment. The heat generation amount W is lower than that of the positive electrode active coating without doping elements.
In particular, the heat generation amount W of the positive electrode active coating per unit mass is less than or equal to 191J/g in the heating treatment process. The heat generation amount W is greatly lower than that of the positive electrode active coating without doping elements.
It is understood that the doping element may be selected from nonmetallic elements capable of occupying a phosphorus atom site or an oxygen atom site in the lithium iron phosphate lattice. In some examples of this embodiment, the doping element may be selected from nitrogen element, silicon element, chlorine element, arsenic element, or selenium element. Experiments prove that the heat production W of the positive electrode plate can be obviously reduced by adopting nitrogen element, silicon element, chlorine element, arsenic element or selenium element.
The magnitude of the reduction in the amount of heat generated by the lithium iron phosphate composite electrode material is also different depending on the kind of doping element. In some examples of this embodiment, the doping element may be selected from a silicon element, a chlorine element, or a nitrogen element.
In some examples of this embodiment, elemental silicon, elemental chlorine, or elemental nitrogen is more effective for reducing the amount of heat generated by the lithium iron phosphate composite electrode material, and can be quite effective at reducing the amount of heat generated by the lithium iron phosphate composite electrode material at a smaller mass content. For example, nitrogen can reduce the heat generation amount W to 160J/g at a mass content of 0.05%, and can reduce the heat generation amount W to 110J/g at a mass content of 0.5%. This can reduce the required material cost while improving the safety of the lithium iron phosphate composite electrode material.
It is understood that additives such as binders and conductive agents may be included in the positive electrode active coating layer in addition to the positive electrode active material to improve charge and discharge performance of the positive electrode active coating layer.
In some examples of this embodiment, the mass ratio of the positive electrode active material in the positive electrode active coating layer may be controlled to be 90% or more.
In some examples of this embodiment, the mass content of the positive electrode active material in the positive electrode active coating layer is 90% -98%. For example, the mass content of the positive electrode active material in the positive electrode active coating layer is 90%, 92%, 94%, 95%, 96% or 98%, and of course, the mass content of the positive electrode active material in the positive electrode active coating layer may be in a range between any two of the above mass contents.
In some examples of this embodiment, the total mass content of binder and conductive agent in the positive electrode active coating is 2% -10%. The total mass content of the binder and the conductive agent in the positive electrode active coating is controlled to be 2% -10%, and the influence of the binder and the conductive agent on heat generation can be reduced as much as possible while the structural stability of the positive electrode active coating in the preparation process is ensured.
In some examples of this embodiment, the mass content of the binder in the positive electrode active coating layer may be 1% -5%.
In some examples of this embodiment, the mass content of the conductive agent in the positive electrode active coating layer may be 1% -5%.
In some examples of this embodiment, the material of the binder may include an organic binding material, for example, the material of the binder may include, but is not limited to, polyvinylidene fluoride.
In some examples of this embodiment, the material of the conductive agent may include a carbon material, for example, the material of the conductive agent may include, but is not limited to, one or more of conductive carbon black, acetylene black, graphene, and carbon nanotubes.
Further, an embodiment of the present disclosure further provides a method for preparing a positive electrode sheet, which includes the following steps: mixing lithium iron phosphate and a precursor containing the doping elements according to a preset proportion, and performing ball milling treatment on the mixture obtained after mixing in a protective gas environment; roasting the mixture subjected to ball milling treatment at a temperature of below 200 ℃ to form the positive electrode active material; and preparing a positive electrode active coating layer comprising the positive electrode active material on the current collector.
In some examples of this embodiment, the doping element may be selected from nonmetallic elements capable of occupying phosphorus atom sites or oxygen atom sites in the lithium iron phosphate lattice. In some examples of this embodiment, the doping element may be selected from nitrogen element, silicon element, chlorine element, arsenic element, or selenium element.
It will be appreciated that the precursor may be selected according to the elemental species of the doping element. For example, the doping element is nitrogen, and the precursor may be selected from one or more of nitrogen-containing compounds, such as ammonium nitrate and lithium nitrate, and the like. As another example, the doping element is elemental silicon, and the precursor may be selected from one or more of silicon-containing compounds, such as lithium silicate and lithium silicon alloys. As another example, the doping element is chlorine, then the precursor may be selected from chlorine-containing compounds, such as one or more of lithium chloride, sodium chloride, and potassium chloride.
Wherein, mixing lithium iron phosphate and precursor containing doping element according to preset proportion means: and selecting lithium iron phosphate and a precursor with corresponding mass according to the required mass content of the lithium iron phosphate in the positive electrode active coating and the mass content of the doping element in the positive electrode active coating.
In some examples of this embodiment, during the ball milling process, the ball milling time may be controlled to be 8h to 24h, so that the precursor and lithium iron phosphate are sufficiently and uniformly mixed.
In some examples of this embodiment, the ambient gas may be a protective gas, i.e., a gas that does not react with the lithium iron phosphate or the precursor during the ball milling process. For example, in this embodiment, the protective gas may be nitrogen or argon.
In some examples of this embodiment, the firing temperature may be controlled to not exceed 200 ℃ during the firing of the ball milled mixture to enable the doping element to replace phosphorus sites and/or oxygen sites in the lithium iron phosphate material and increase the lattice volume. For example, in the process of roasting the mixture after the ball milling treatment, the roasting temperature may be controlled to be 100 ℃ to 190 ℃. Further, the roasting temperature can be controlled to be 150-190 ℃.
In some examples of this embodiment, prior to subjecting the mixture after ball milling to the calcination treatment, further comprising: and (3) screening the mixture after ball milling treatment, and retaining powder with the particle size less than or equal to 20 mu m. The powder with smaller particle size is mixed more uniformly in the ball milling process, which is favorable for replacing phosphorus atoms and/or oxygen atom sites in the roasting process by doping elements, so that the doping elements are distributed more uniformly, the crystallinity of the powder is better, and the structural stability of the obtained electrode active material is further improved.
In some examples of this embodiment, the method of preparing the positive electrode active coating layer further includes a step of mixing an electrode active material with a conductive agent and a binder.
In some examples of this embodiment, the total mass content of the binder and the conductive agent in the positive electrode active coating is 2% -10%. The total mass content of the binder and the conductive agent in the positive electrode active coating is controlled to be 2% -10%, and the influence of the binder and the conductive agent on heat generation can be reduced as much as possible while the structural stability of the positive electrode active coating in the preparation process is ensured.
In some examples of this embodiment, the material of the conductive agent may include a carbon material, for example, the material of the conductive agent may include, but is not limited to, one or more of conductive carbon black, acetylene black, graphene, and carbon nanotubes.
In some examples of this embodiment, the material of the binder may include an organic binding material, for example, the material of the binder may include, but is not limited to, polyvinylidene fluoride.
In some examples of this embodiment, the doping element is present in the positive active coating in an amount of 0.001% -8% by mass.
Further, the mass content of the doping element in the positive electrode active coating is 0.05% -4%. Further, the mass content of the doping element in the positive electrode active coating is 0.5% -1%.
In some examples of this embodiment, the heat generation amount per unit mass of the positive electrode active coating is 249J/g or less.
Further, the heat generation amount of the positive electrode active coating layer per unit mass is less than or equal to 208J/g. Further, the heat generation amount of the positive electrode active coating layer per unit mass is less than or equal to 191J/g. Wherein the heat generation amount W is the total heat released by the positive electrode active coating in unit mass in the heating process.
It is understood that the positive electrode active coating layer may be prepared from raw materials including an electrode active material. For example, the electrode active material may be dispersed in a dispersing agent to prepare a slurry, and then the slurry is prepared into a positive electrode active coating layer by means of coating and drying.
In some examples of this embodiment, the dispersant is removed during the drying process, and thus the positive electrode active coating layer may include only the above-described electrode active material.
For the positive electrode, the heat generation amount of the positive electrode active coating in the thermal decomposition process can be reduced, so that the positive electrode also has higher safety performance.
Further, one embodiment of the present disclosure also provides a battery including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode and the negative electrode are disposed opposite to each other, the electrolyte is disposed between the positive electrode and the negative electrode, and the electrolyte is used to conduct lithium ions. The positive electrode may be the positive electrode sheet in the above embodiment.
With respect to the battery, since the heat generation amount of the positive electrode in the thermal decomposition process is relatively low, the heat generation amount of the battery in the thermal decomposition process or the thermal runaway process can also be effectively reduced, and thus the battery also has high safety.
It will be appreciated that the battery may be a lithium ion battery.
Further, in order to facilitate understanding of the embodiments of the positive electrode tab of the present disclosure and advantages thereof, the present disclosure also provides the following examples and comparative examples.
Example 1.1
Mixing 91.999 parts by mass of pure-phase lithium iron phosphate material and silicon-lithium alloy containing 0.001 part by mass of silicon element, placing the mixture in a ball milling tank, introducing nitrogen as protective gas, and performing ball milling treatment for 16 hours;
taking out the mixed powder obtained after ball milling treatment, screening out powder with the particle size below 100 μm, and roasting at 180 ℃ to form an anode active material;
adopting Nitrogen Methyl Pyrrolidone (NMP) as a dispersing agent, adding the positive electrode active substance, polyvinylidene fluoride and conductive carbon black into the dispersing agent according to the proportion of 92:4:4 for uniform dispersion, coating the slurry on aluminum foil with the thickness of 12 mu m, and then forming a positive electrode plate through vacuum drying and rolling;
and a metal lithium sheet is used as a negative electrode sheet, and a polypropylene diaphragm with the thickness of 12 mu m, an electrolyte and a prepared positive electrode sheet are combined to form the button cell, wherein the solvent of the electrolyte is a mixture of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Vinylene Carbonate (VC), and the volume ratio of the EC to the DMC to the VC is 1:1:1.
Example 1.2
Substantially the same as in example 1.1, the main differences are: 91.99 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 0.01 parts by mass of silicon element are adopted.
Example 1.3
Substantially the same as in example 1.1, the main differences are: 91.95 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 0.05 parts by mass of silicon element were employed.
Example 1.4
Substantially the same as in example 1.1, the main differences are: 91.5 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 0.5 parts by mass of silicon element are adopted.
Example 1.5
Substantially the same as in example 1.1, the main differences are: 91 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 1 part by mass of silicon element are adopted.
Example 1.6
Substantially the same as in example 1.1, the main differences are: 88 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 4 parts by mass of silicon element are adopted.
Example 1.7
Substantially the same as in example 1.1, the main differences are: 84 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 8 parts by mass of silicon element were used.
Comparative example 1
Substantially the same as in example 1.1, the main differences are: 82 parts by mass of a pure-phase lithium iron phosphate material and a silicon lithium alloy containing 10 parts by mass of silicon element were used.
Example 2.1
Mixing 91.999 parts by mass of pure-phase lithium iron phosphate material and 0.001 part by mass of lithium chloride containing chlorine element, placing the mixture in a ball milling tank, introducing nitrogen as protective gas, and performing ball milling treatment for 16 hours;
taking out the mixed powder obtained after ball milling treatment, screening out powder with the particle size below 20 mu m, and roasting at 180 ℃ to form an anode active material;
adopting Nitrogen Methyl Pyrrolidone (NMP) as a dispersing agent, adding the positive electrode active substance, polyvinylidene fluoride and conductive carbon black into the dispersing agent according to the proportion of 92:4:4 for uniform dispersion, coating the slurry on aluminum foil with the thickness of 12 mu m, and then forming a positive electrode plate through vacuum drying and rolling;
and a metal lithium sheet is used as a negative electrode sheet, and a polypropylene diaphragm with the thickness of 12 mu m, an electrolyte and a prepared positive electrode sheet are combined to form the button cell, wherein the solvent of the electrolyte is a mixture of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Vinylene Carbonate (VC), and the volume ratio of the EC to the DMC to the VC is 1:1:1.
Example 2.2
Substantially the same as in example 2.1, the main differences are: 91.99 parts by mass of a pure-phase lithium iron phosphate material and 0.01 part by mass of lithium chloride containing chlorine element were used.
Example 2.3
Substantially the same as in example 2.1, the main differences are: 91.95 parts by mass of a pure-phase lithium iron phosphate material and 0.05 part by mass of lithium chloride containing chlorine element were used.
Example 2.4
Substantially the same as in example 2.1, the main differences are: 91.5 parts by mass of a pure-phase lithium iron phosphate material and 0.5 part by mass of lithium chloride containing chlorine element were used.
Example 2.5
Substantially the same as in example 2.1, the main differences are: 91 parts by mass of a pure-phase lithium iron phosphate material was used, and 1 part by mass of lithium chloride containing chlorine was used.
Example 2.6
Substantially the same as in example 2.1, the main differences are: 88 parts by mass of a pure-phase lithium iron phosphate material was used, and 4 parts by mass of lithium chloride containing chlorine was contained.
Example 2.7
Substantially the same as in example 2.1, the main differences are: 84 parts by mass of a pure-phase lithium iron phosphate material and 8 parts by mass of lithium chloride containing chlorine element were used.
Comparative example 2
Substantially the same as in example 2.1, the main differences are: 82 parts by mass of a pure-phase lithium iron phosphate material was used, and 10 parts by mass of lithium chloride containing chlorine was used.
Example 3.1
Mixing 91.999 parts by mass of pure-phase lithium iron phosphate material and 0.001 part by mass of arsenic lithium arsenate, placing the mixture in a ball milling tank, introducing nitrogen as protective gas, and performing ball milling treatment for 16 hours;
taking out the mixed powder obtained after ball milling treatment, screening out powder with the particle size below 20 mu m, and roasting at 180 ℃ to form an anode active material;
adopting Nitrogen Methyl Pyrrolidone (NMP) as a dispersing agent, adding the positive electrode active substance, polyvinylidene fluoride and conductive carbon black into the dispersing agent according to the proportion of 92:4:4 for uniform dispersion, coating the slurry on aluminum foil with the thickness of 12 mu m, and then forming a positive electrode plate through vacuum drying and rolling;
and a metal lithium sheet is used as a negative electrode sheet, and a polypropylene diaphragm with the thickness of 12 mu m, an electrolyte and a prepared positive electrode sheet are combined to form the button cell, wherein the solvent of the electrolyte is a mixture of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Vinylene Carbonate (VC), and the volume ratio of the EC to the DMC to the VC is 1:1:1.
Example 3.2
Substantially the same as in example 3.1, the main differences are: 91.99 parts by mass of a pure-phase lithium iron phosphate material and 0.01 parts by mass of lithium arsenate containing arsenic element were used.
Example 3.3
Substantially the same as in example 3.1, the main differences are: 91.95 parts by mass of a pure-phase lithium iron phosphate material and 0.05 part by mass of lithium arsenate containing arsenic element were used.
Example 3.4
Substantially the same as in example 3.1, the main differences are: 91.5 parts by mass of a pure-phase lithium iron phosphate material and 0.5 parts by mass of lithium arsenate containing arsenic element were used.
Example 3.5
Substantially the same as in example 3.1, the main differences are: 91 parts by mass of a pure-phase lithium iron phosphate material was used, and 1 part by mass of lithium arsenate containing arsenic element was used.
Example 3.6
Substantially the same as in example 3.1, the main differences are: 88 parts by mass of a pure-phase lithium iron phosphate material was used, and 4 parts by mass of lithium arsenate containing arsenic element was used.
Example 3.7
Substantially the same as in example 3.1, the main differences are: 84 parts by mass of a pure-phase lithium iron phosphate material was used, and 8 parts by mass of lithium arsenate was contained.
Comparative example 3
Substantially the same as in example 3.1, the main differences are: 82 parts by mass of a pure-phase lithium iron phosphate material was used, and 10 parts by mass of lithium arsenate containing arsenic element was used.
Example 4.1
Mixing 91.999 parts by mass of pure-phase lithium iron phosphate material and 0.001 part by mass of lithium nitrate containing nitrogen element, placing the mixture in a ball milling tank, introducing nitrogen as protective gas, and performing ball milling treatment for 16 hours;
taking out the mixed powder obtained after ball milling treatment, screening out powder with the particle size below 20 mu m, and roasting at 180 ℃ to form an anode active material;
adopting Nitrogen Methyl Pyrrolidone (NMP) as a dispersing agent, adding the positive electrode active substance, polyvinylidene fluoride and conductive carbon black into the dispersing agent according to the proportion of 92:4:4 for uniform dispersion, coating the slurry on aluminum foil with the thickness of 12 mu m, and then forming a positive electrode plate through vacuum drying and rolling;
and a metal lithium sheet is used as a negative electrode sheet, and a polypropylene diaphragm with the thickness of 12 mu m, an electrolyte and a prepared positive electrode sheet are combined to form the button cell, wherein the solvent of the electrolyte is a mixture of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Vinylene Carbonate (VC), and the volume ratio of the EC to the DMC to the VC is 1:1:1.
Example 4.2
Substantially the same as in example 4.1, the main differences are: 91.99 parts by mass of a pure-phase lithium iron phosphate material and 0.01 parts by mass of lithium nitrate containing nitrogen element were used.
Example 4.3
Substantially the same as in example 4.1, the main differences are: 91.95 parts by mass of a pure-phase lithium iron phosphate material and 0.05 part by mass of lithium nitrate containing nitrogen element were used.
Example 4.4
Substantially the same as in example 4.1, the main differences are: 91.5 parts by mass of a pure-phase lithium iron phosphate material and 0.5 parts by mass of lithium nitrate containing nitrogen element were used.
Example 4.5
Substantially the same as in example 4.1, the main differences are: 91 parts by mass of a pure-phase lithium iron phosphate material and 1 part by mass of lithium nitrate containing nitrogen element were used.
Example 4.6
Substantially the same as in example 4.1, the main differences are: 88 parts by mass of a pure-phase lithium iron phosphate material and 4 parts by mass of lithium nitrate containing nitrogen element were used.
Example 4.7
Substantially the same as in example 4.1, the main differences are: 84 parts by mass of a pure-phase lithium iron phosphate material and 8 parts by mass of lithium nitrate containing nitrogen element were used.
Comparative example 4
Substantially the same as in example 4.1, the main differences are: 82 parts by mass of a pure-phase lithium iron phosphate material and 10 parts by mass of lithium nitrate containing nitrogen element were used.
Comparative example 5
92 pure-phase lithium iron phosphate material is adopted as an anode active material;
adopting Nitrogen Methyl Pyrrolidone (NMP) as a dispersing agent, adding the positive electrode active substance, polyvinylidene fluoride and conductive carbon black into the dispersing agent according to the proportion of 92:4:4 for uniform dispersion, coating the slurry on aluminum foil with the thickness of 12 mu m, and then forming a positive electrode plate through vacuum drying and rolling;
and a metal lithium sheet is used as a negative electrode sheet, and a polypropylene diaphragm with the thickness of 12 mu m, an electrolyte and a prepared positive electrode sheet are combined to form the button cell, wherein the solvent of the electrolyte is a mixture of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Vinylene Carbonate (VC), and the volume ratio of the EC to the DMC to the VC is 1:1:1.
Test 1: the batteries prepared in each of the above examples and comparative examples were charged and discharged at a rate of 0.1C in a voltage range of 3V to 4.2V to complete interface activation, and then the batteries were charged at 0.1C to 4.2V and then charged at a constant voltage of 4.2V for 10min, and then the charging was stopped. And (3) splitting the battery, taking out the positive electrode plate, scraping the positive electrode active coating on the electrode plate, cleaning twice by adopting dimethyl carbonate, drying, and weighing the mass m. Transferring the material of the positive electrode active coating into a Differential Scanning Calorimeter (DSC) to start heating treatment, setting the flow rate of nitrogen to be 50mL/min, heating the material of the positive electrode active coating to 30 ℃, standing for 10min, heating to 400 ℃ at the heating rate of 5 ℃/min, and testing the overall heat generation quantity Q of the material of the electrode active layer in the process. The heat generation amount W per unit mass is defined as the ratio of the total heat generation amount Q to the mass m in J/g. The test results can be seen in table 1, in which M represents the mass content of the doping element in the positive electrode active coating layer, and W represents the heat generation amount per unit mass of the positive electrode active coating layer.
TABLE 1
Referring to Table 1, it is understood that comparative example 5 does not use a doping element, and the heat generation amount W per unit mass of the positive electrode active coating layer is 258J/g. In examples 1.1 to 4.7, different nonmetallic elements are used as doping elements, and the mass content M of the nonmetallic elements is 0.001% -8%, so that the heat generation amount W of the positive electrode active coating per unit mass can be reduced.
Wherein, when the mass content M of the doping element is between 0.05% and 4%, the heat generation amount W per unit mass is less than or equal to 208J/g, namely, the heat generation amount W per unit mass is obviously reduced, and compared with comparative example 5, the heat generation amount W per unit mass is reduced by more than 50J/g. In particular, when the mass content M of the doping element is 0.5% -1%, the heat generation amount W per unit mass is smaller than or equal to 169J/g, namely, the heat generation amount W per unit mass is remarkably reduced by more than 89J/g compared with comparative example 5.
In addition, the nitrogen element and the chlorine element have a significantly better effect in reducing the amount of heat generated per unit mass than other nonmetallic elements.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The positive pole piece is characterized by comprising a current collector and a positive pole active coating, wherein the positive pole active coating is arranged on the current collector;
the positive electrode active coating comprises a positive electrode active substance, the mass content of the positive electrode active substance in the positive electrode active coating is more than 90%, the positive electrode active substance is a pure-phase lithium iron phosphate material containing doping elements, the doping elements are arsenic elements, the mass percentage content M of the doping elements in the positive electrode active coating ranges from 0.5% to 1%, the heat generation amount W of the positive electrode active coating per unit mass is less than or equal to 169J/g, and the heat generation amount W is DSC heat release amount of the positive electrode active coating per unit mass in the nitrogen atmosphere at the temperature rising speed of 5K/min in the temperature rising process within the temperature range of 30-400 ℃.
2. The positive electrode sheet according to claim 1, wherein the mass content of the positive electrode active material in the positive electrode active coating layer is 90% -98%.
3. The positive electrode sheet according to any one of claims 1 to 2, wherein the positive electrode active coating further comprises a binder and a conductive agent, and the total mass content of the binder and the conductive agent in the positive electrode active coating is 2% -10%.
4. A positive electrode sheet according to claim 3, wherein the binder material comprises polyvinylidene fluoride.
5. The positive electrode sheet according to claim 3, wherein the material of the conductive agent comprises one or more of conductive carbon black, acetylene black, graphene, and carbon nanotubes.
6. The positive electrode sheet according to claim 3, wherein the mass content of the binder in the positive electrode active coating layer is 1% -5%.
7. The positive electrode sheet according to claim 3, wherein the mass content of the conductive agent in the positive electrode active coating layer is 1% -5%.
8. A method for preparing the positive electrode sheet according to any one of claims 1 to 7, comprising the steps of:
mixing lithium iron phosphate and a precursor containing the doping elements according to a preset proportion, and performing ball milling treatment on the mixture obtained after mixing in a protective gas environment;
roasting the mixture subjected to ball milling treatment at a temperature of below 200 ℃ to form the positive electrode active material;
the positive electrode active coating layer including the positive electrode active material is prepared on the current collector.
9. The method of claim 8, further comprising, prior to calcining the mixture after ball milling: and (3) screening the mixture after ball milling treatment, and retaining powder with the particle size less than or equal to 20 mu m.
10. A battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is disposed opposite to the negative electrode, the electrolyte is disposed between the positive electrode and the negative electrode, and the positive electrode comprises the positive electrode sheet according to any one of claims 1 to 7.
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| Improvement of electrochemical properties of LiFePO 4 /C cathode materials by chlorine doping;Lin Yang;《J Solid State Electrochem 》;实验部分 * |
| Tuning a small electron polaron in FePO4 by P-site or O-site doping based on DFT+Uand KMC simulation;Taowen Chen等;《Phys. Chem. Chem. Phys》;第3部分以及表1-2 * |
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