CN116332149A - Preparation method for improving low-temperature stability of lithium iron manganese phosphate - Google Patents
Preparation method for improving low-temperature stability of lithium iron manganese phosphate Download PDFInfo
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- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 24
- 239000011248 coating agent Substances 0.000 claims abstract description 23
- 238000000576 coating method Methods 0.000 claims abstract description 23
- 239000002243 precursor Substances 0.000 claims abstract description 19
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 18
- 239000008367 deionised water Substances 0.000 claims abstract description 18
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 18
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- KFDVPJUYSDEJTH-UHFFFAOYSA-N 4-ethenylpyridine Chemical compound C=CC1=CC=NC=C1 KFDVPJUYSDEJTH-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000011259 mixed solution Substances 0.000 claims abstract description 17
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims abstract description 16
- 229930006000 Sucrose Natural products 0.000 claims abstract description 16
- 239000002245 particle Substances 0.000 claims abstract description 16
- 239000005720 sucrose Substances 0.000 claims abstract description 16
- 238000001132 ultrasonic dispersion Methods 0.000 claims abstract description 16
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims abstract description 15
- 229960001781 ferrous sulfate Drugs 0.000 claims abstract description 13
- 235000003891 ferrous sulphate Nutrition 0.000 claims abstract description 13
- 239000011790 ferrous sulphate Substances 0.000 claims abstract description 13
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract description 13
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims abstract description 13
- 229940099596 manganese sulfate Drugs 0.000 claims abstract description 13
- 235000007079 manganese sulphate Nutrition 0.000 claims abstract description 13
- 239000011702 manganese sulphate Substances 0.000 claims abstract description 13
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 claims abstract description 13
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 239000012299 nitrogen atmosphere Substances 0.000 claims abstract description 10
- 238000001694 spray drying Methods 0.000 claims abstract description 10
- 238000000227 grinding Methods 0.000 claims abstract description 9
- 239000002086 nanomaterial Substances 0.000 claims abstract description 9
- 238000001354 calcination Methods 0.000 claims abstract description 8
- 229940068918 polyethylene glycol 400 Drugs 0.000 claims abstract description 8
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 claims abstract description 7
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 claims abstract description 7
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims abstract description 6
- 239000000843 powder Substances 0.000 claims abstract 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 2
- 239000011572 manganese Substances 0.000 claims description 2
- 239000007774 positive electrode material Substances 0.000 abstract description 7
- 238000010298 pulverizing process Methods 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 18
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 238000013329 compounding Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical group O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 150000001721 carbon Chemical class 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 description 1
- -1 4-vinyl pyridine compound Chemical class 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N NMP Substances CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000004005 microsphere Substances 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Nanotechnology (AREA)
- Physics & Mathematics (AREA)
- Composite Materials (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to a preparation method for improving low-temperature stability of lithium iron manganese phosphate, which belongs to the technical field of positive electrode materials and comprises the following steps: A. adding lithium hydroxide monohydrate, manganese sulfate and ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion, reacting for 1-2h at 150-170 ℃, and then reacting for at least 6h at 200-220 ℃ to obtain a precursor; B. mixing melamine, 4-vinyl pyridine, sucrose and deionized water in pure nitrogen atmosphere to obtain a mixed solution, heating the mixed solution at 200-250 ℃ for 20-30min under stirring, then heating to 500-600 ℃ at the speed of 4-6 ℃/min, maintaining for 1-2h, drying, and pulverizing to the particle size of 100-200nm to obtain a powdery coating; C. and B, adding the powder coating obtained in the step B into sodium dodecyl benzene sulfonate and deionized water for mixing, then adding the precursor obtained in the step A, performing ultrasonic dispersion, spray drying, calcining, and grinding to the particle size of 100-200nm to obtain the nano material. The lithium iron manganese phosphate prepared by the preparation method disclosed by the invention has good low-temperature stability.
Description
Technical Field
The invention belongs to the technical field of positive electrode materials, and particularly relates to a preparation method for improving low-temperature stability of lithium iron manganese phosphate.
Background
Lithium batteries have been widely used in mobile phones, notebook computers, electric bicycles, electric vehicles, and the like as high-energy green energy sources in the key research fields of new energy development. Along with the expansion of application fields, the requirements on the energy density and the safety performance of the lithium ion storage battery are higher and higher. The positive electrode of the lithium ion storage battery is always a key for improving the performance of the battery, and the low-temperature stability of the positive electrode has a key influence on the charge-discharge cycle performance of the battery.
Lithium iron manganese phosphate has attracted extensive attention and research since it was proposed as a positive electrode material for lithium iron phosphate "upgrades". The lithium iron manganese phosphate integrates the advantages of the lithium iron phosphate and the ternary material, and the production process is similar to that of the lithium iron phosphate, the cost is low, and the competitive advantage of the lithium iron manganese phosphate is continuously strengthened along with the development of capacity release, process optimization and modification technology. However, the current lithium iron manganese phosphate has a lower capacity retention rate at-20 ℃, especially at-40 ℃, which is lower and reaches below 20%.
Disclosure of Invention
The invention aims to solve the technical problem of improving the low-temperature stability of lithium manganese iron phosphate.
The invention adopts the technical scheme for realizing the purpose:
the preparation method for improving the low-temperature stability of the lithium iron manganese phosphate comprises the following steps:
A. adding lithium hydroxide monohydrate, manganese sulfate and ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 1-2h, reacting for 1-2h at 150-170 ℃, and then reacting for at least 6h at 200-220 ℃ to obtain a precursor;
B. under the pure nitrogen atmosphere, mixing melamine, 4-vinyl pyridine, sucrose and deionized water to obtain a mixed solution, wherein the mass ratio of the total amount of the melamine to the 4-vinyl pyridine to the sucrose is (10-20): 1, heating the mixed solution for 20-30min at 200-250 ℃ under stirring, then heating to 500-600 ℃ at the speed of 4-6 ℃/min, keeping for 1-2h, drying, and crushing to the particle size of 100-200nm to obtain a powdery coating body;
C. adding sodium dodecyl benzene sulfonate and deionized water into the powdery coating obtained in the step B, mixing, adding the precursor obtained in the step A, performing ultrasonic dispersion for 30-60min, spray drying, calcining at 700-800 ℃ for at least 6h under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
Further, the molar ratio of the lithium hydroxide monohydrate, the manganese sulfate and the ferrous sulfate is 1: (0.6-0.7): (0.3-0.4), and n (Mn) +n (Fe) =1.
Further, the mass ratio of melamine to 4-vinylpyridine is (7-8): 2-3.
Further, the sucrose is used in an amount of 0.1 to 0.15 of the molar amount of the lithium hydroxide monohydrate.
Further, the sodium dodecyl benzene sulfonate is 1% -2% of the precursor mass obtained in the step A.
Further, the spray drying temperature is 120-200 ℃.
The beneficial effects of the invention are as follows:
the lithium iron manganese phosphate anode material prepared by the preparation method is nanoscale, and the binding force between the carbon coating and the lithium iron manganese phosphate can be improved by co-doping modification of melamine and 4-vinyl pyridine on the carbon coating, so that the coating effect is improved, the electron conductivity and the ion diffusion coefficient are improved, and the low-temperature stability performance of the lithium iron manganese phosphate anode material can be obviously improved.
According to the invention, the nano material is obtained by grinding to the particle size of 100-200nm, so that the migration path of particles is shortened, and the low-temperature stability of the lithium iron manganese phosphate positive electrode material is further improved.
Detailed Description
The present invention will be described in detail with reference to specific examples. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
1. Detailed description of the preferred embodiments
Example 1
The preparation method for improving the low-temperature stability of the lithium iron manganese phosphate comprises the following steps:
A. 42g of LiOH H are taken 2 Adding 91g of manganese sulfate, 112g of ferrous sulfate and 10% of aqueous solution of O into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 1h, reacting for 2h at 150 ℃, and then reacting for 10h at 200 ℃ to obtain a precursor;
B. under pure nitrogen atmosphere, 241.5g of melamine, 103.5g of 4-vinyl pyridine and 34.5g of sucrose are taken and added with deionized water to be mixed to obtain a mixed solution, the mixed solution is heated for 30min under the condition of stirring, then the temperature is raised to 500 ℃ at the speed of 4 ℃/min, the mixture is kept for 1h, and the mixture is dried and crushed to the grain size of 100-200nm to obtain a powdery coating body;
C. adding sodium dodecyl benzene sulfonate and deionized water into the powdery coating obtained in the step B, mixing, adding the sodium dodecyl benzene sulfonate which is 1% of the mass of the powdery coating obtained in the step B, adding the precursor obtained in the step A, performing ultrasonic dispersion for 30min, performing spray drying at 120 ℃, calcining for 8h at 700 ℃ under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
Example 2
The preparation method for improving the low-temperature stability of the lithium iron manganese phosphate comprises the following steps:
A. 42g of LiOH H are taken 2 Preparing an aqueous solution with the mass concentration of 10%, 106g of manganese sulfate and 83.5g of ferrous sulfate, adding the aqueous solution, the manganese sulfate and the ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 1.5h, reacting for 1.5h at 160 ℃, and then reacting for 8h at 210 ℃ to obtain a precursor;
B. adding 492g of melamine, 123g of 4-vinylpyridine and 41g of sucrose into deionized water under pure nitrogen atmosphere, mixing to obtain a mixed solution, heating the mixed solution at 230 ℃ for 20min under stirring, then heating to 600 ℃ at a speed of 5 ℃/min, maintaining for 1.5h, drying, and crushing to a particle size of 100-200nm to obtain a powdery coating;
C. adding sodium dodecyl benzene sulfonate and deionized water into the powdery coating obtained in the step B, mixing, adding the sodium dodecyl benzene sulfonate which is 2% of the mass of the powdery coating obtained in the step B, adding the precursor obtained in the step A, performing ultrasonic dispersion for 40min, performing spray drying at 150 ℃, calcining for 6h at 800 ℃ under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
Example 3
The preparation method for improving the low-temperature stability of the lithium iron manganese phosphate comprises the following steps:
A. 42g of LiOH H are taken 2 Adding 91g of manganese sulfate, 112g of ferrous sulfate and 10% of aqueous solution of O into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 2h, reacting at 170 ℃ for 1h, and reacting at 220 ℃ for 10h to obtain a precursor;
B. adding 721g of melamine, 309g of 4-vinyl pyridine and 51.5g of sucrose into deionized water under a pure nitrogen atmosphere, mixing to obtain a mixed solution, heating the mixed solution at 250 ℃ for 25min under the stirring condition, then heating to 550 ℃ at the speed of 6 ℃/min, maintaining for 2h, drying, and crushing to the particle size of 100-200nm to obtain a powdery coating body;
C. adding sodium dodecyl benzene sulfonate and deionized water into the powdery coating obtained in the step B, mixing, wherein the sodium dodecyl benzene sulfonate accounts for 1.5% of the mass of the powdery coating obtained in the step B, adding the precursor obtained in the step A, performing ultrasonic dispersion for 50min, performing spray drying at 180 ℃, calcining for 7h at 750 ℃ under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
Example 4
The preparation method for improving the low-temperature stability of the lithium iron manganese phosphate comprises the following steps:
A. 42g of LiOH H are taken 2 Preparing an aqueous solution with the mass concentration of 10%, 106g of manganese sulfate and 83.5g of ferrous sulfate, adding the aqueous solution, the manganese sulfate and the ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 1.5h, reacting for 1.5h at 165 ℃, and then reacting for 9h at 210 ℃ to obtain a precursor;
B. under the pure nitrogen atmosphere, adding 289.8g of melamine, 124.2g of 4-vinyl pyridine and 34.5g of sucrose into deionized water, mixing to obtain a mixed solution, heating the mixed solution under the condition of stirring at 220 ℃ for 25min, then heating to 580 ℃ at the rate of 5 ℃/min, keeping for 1.5h, drying, and crushing to the particle size of 100-200nm to obtain a powdery coating body;
C. adding sodium dodecyl benzene sulfonate and deionized water into the powdery coating obtained in the step B, mixing, wherein the sodium dodecyl benzene sulfonate is 1.2% of the mass of the powdery coating obtained in the step B, then adding the precursor obtained in the step A, performing ultrasonic dispersion for 60min, performing spray drying at 200 ℃, calcining for 9h at 750 ℃ under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
Comparative example 1
The difference from example 2 is that: in the step B, 615g of melamine and 41g of sucrose are taken under the pure nitrogen atmosphere, and deionized water is added for mixing to obtain a mixed solution.
Comparative example 2
The difference from example 2 is that: in the step B, 615g of 4-vinyl pyridine and 41g of sucrose are taken under the pure nitrogen atmosphere, and deionized water is added for mixing to obtain a mixed solution.
Comparative example 3
The difference from example 2 is that: in the step B, 820g of melamine, 205g of 4-vinylpyridine and 41g of sucrose are added into deionized water under the pure nitrogen atmosphere to obtain a mixed solution.
Comparative example 4
The preparation method of the lithium iron manganese phosphate comprises the following steps:
A. 42g of LiOH H are taken 2 Preparing an aqueous solution with the mass concentration of 10%, 106g of manganese sulfate and 83.5g of ferrous sulfate, adding the aqueous solution, the manganese sulfate and the ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion for 1.5h, reacting for 1.5h at 160 ℃, and then reacting for 8h at 210 ℃ to obtain a precursor;
B. adding the precursor into sodium dodecyl benzene sulfonate and deionized water, mixing, wherein the mass of the sodium dodecyl benzene sulfonate is 2% of that of the precursor, performing ultrasonic dispersion for 40min, performing spray drying at 150 ℃, calcining at 800 ℃ for 6h under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
2. Performance experiments
Taking examples 1-4 and comparative examples 1-3 as positive electrode materials, taking mesophase carbon microspheres as negative electrodes, distributing positive and negative electrode current collectors as aluminum foils and copper foils, adopting ceramic diaphragms as diaphragms, and injecting 1mol/L of LiPF (lithium ion battery) 6 Composition of ethylene carbonate and 1, 3-propane sultoneThe electrolyte of (ethylene carbonate and 1, 3-propane sultone volume ratio 1:1) was assembled into a soft-packed battery in a glove box, and the battery was allowed to stand for 8 hours and then tested.
1. Low temperature performance
The battery was activated by charging and discharging at a constant temperature of 25℃at room temperature at a rate of 0.1C of 2.5V to 4.3V, followed by charging and discharging at 1C for cycles at-20℃and-40℃respectively, and the test results are shown in Table 1.
TABLE 1
From the comparison of the example 2 in table 1 with the comparative example 1 and the comparative example 2, it can be seen that the modified carbon coating layer obtained by independently doping the melamine and the 4-vinylpyridine in the compounding doping ratio has better low-temperature stability after coating the lithium manganese iron phosphate; comparing with comparative example 3, it can be seen that the compounding ratio of melamine and 4-vinylpyridine is controlled to be 1-2% of sucrose, otherwise the low temperature stability is poor; compared with comparative example 4, the invention has better low-temperature stability than the carbon-coated lithium iron manganese phosphate.
2. Charge-discharge capacity performance experiment
The charge and discharge capacity was measured by charging to 4.3V at 0.1C rate and then discharging to 2.5V at 0.1C rate at a cutoff current of 0.01C at room temperature, and the results are shown in table 2.
TABLE 2
| Project | Charging capacity (mAh/g) | Discharge capacity (mAh/g) |
| Example 1 | 165.2 | 160.5 |
| Example 2 | 170.3 | 164.2 |
| Example 3 | 168.1 | 161.3 |
| Example 4 | 166.4 | 162.7 |
| Comparative example 1 | 150.8 | 141.6 |
| Comparative example 2 | 152.6 | 150.1 |
| Comparative example 3 | 144.7 | 138.2 |
| Comparative example 4 | 141.3 | 134.4 |
From the comparison of the example 2 with the comparative example 1 and the comparative example 2 in the table 2, it can be seen that the melamine and 4-vinyl pyridine compound doped modified carbon coating layer has better low-temperature stability after coating the lithium manganese iron phosphate; compared with comparative example 3, it can be seen that the compounding ratio of melamine and 4-vinylpyridine is controlled to be 1-2% of sucrose, so that the charge-discharge capacity performance of the material can be improved; comparing with comparative example 4, it can be seen that the charge-discharge capacity of the present invention is better than that of the carbon-coated lithium manganese iron phosphate.
3. Resistivity test
The positive electrode materials of examples 1 to 4 and comparative examples 1 to 3 were stirred with acetylene black, NMP and PVDF, respectively, to form pastes, dried, ground to 100 to 200nm, and tested for resistivity by a four-probe resistivity tester, and the results were shown in Table 3.
TABLE 3 Table 3
As can be seen from Table 3, the resistivity of the lithium iron manganese phosphate positive electrode material prepared by the method is obviously improved.
Claims (6)
1. The preparation method for improving the low-temperature stability of the lithium iron manganese phosphate is characterized by comprising the following steps of:
A. adding lithium hydroxide monohydrate, manganese sulfate and ferrous sulfate into polyethylene glycol 400, mixing, performing ultrasonic dispersion, reacting for 1-2h at 150-170 ℃, and then reacting for at least 6h at 200-220 ℃ to obtain a precursor;
B. under the pure nitrogen atmosphere, mixing melamine, 4-vinyl pyridine, sucrose and deionized water to obtain a mixed solution, wherein the mass ratio of the total amount of the melamine to the 4-vinyl pyridine to the sucrose is (10-20): 1, heating the mixed solution for 20-30min at 200-250 ℃ under stirring, then heating to 500-600 ℃ at the speed of 4-6 ℃/min, keeping for 1-2h, drying, and crushing to the particle size of 100-200nm to obtain a powdery coating body;
C. and C, adding the powder coating obtained in the step B into sodium dodecyl benzene sulfonate and deionized water for mixing, adding the precursor obtained in the step A, performing ultrasonic dispersion, spray drying, calcining at 700-800 ℃ for at least 6 hours under the protection of nitrogen, and grinding to the particle size of 100-200nm to obtain the nano material.
2. The preparation method for improving the low-temperature stability of lithium iron manganese phosphate according to claim 1, wherein the molar ratio of lithium hydroxide monohydrate, manganese sulfate and ferrous sulfate is 1: (0.6-0.7): (0.3-0.4), and n (Mn) +n (Fe) =1.
3. The preparation method for improving the low-temperature stability of lithium iron manganese phosphate according to claim 1, wherein the mass ratio of melamine to 4-vinylpyridine is (7-8): 2-3.
4. The method for improving the low-temperature stability of lithium manganese iron phosphate according to claim 1, wherein the amount of sucrose is 0.1-0.15 of the molar amount of lithium hydroxide monohydrate.
5. The method for improving low-temperature stability of lithium iron manganese phosphate according to claim 1, wherein sodium dodecyl benzene sulfonate is 1% -2% of the mass of the precursor obtained in the step A.
6. The method for preparing the lithium iron manganese phosphate with improved low-temperature stability according to claim 1, wherein the spray drying temperature is 120-200 ℃.
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| CN109244391A (en) * | 2018-08-22 | 2019-01-18 | 江苏元景锂粉工业有限公司 | A kind of nitrogen mixes carbon coating iron manganese phosphate lithium material and preparation method thereof |
| CN109473675A (en) * | 2018-12-19 | 2019-03-15 | 中科廊坊过程工程研究院 | A kind of cladded type lithium ferric manganese phosphate positive electrode and its preparation method and application |
| US20200119339A1 (en) * | 2018-10-15 | 2020-04-16 | GM Global Technology Operations LLC | Method for making silicon-containing composite electrodes for lithium-based batteries |
| CN112885995A (en) * | 2021-04-02 | 2021-06-01 | 河北九丛科技有限公司 | Manufacturing method of lithium ferric manganese phosphate coated high-voltage lithium nickel manganese oxide positive electrode material |
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| CN109244391A (en) * | 2018-08-22 | 2019-01-18 | 江苏元景锂粉工业有限公司 | A kind of nitrogen mixes carbon coating iron manganese phosphate lithium material and preparation method thereof |
| US20200119339A1 (en) * | 2018-10-15 | 2020-04-16 | GM Global Technology Operations LLC | Method for making silicon-containing composite electrodes for lithium-based batteries |
| CN109473675A (en) * | 2018-12-19 | 2019-03-15 | 中科廊坊过程工程研究院 | A kind of cladded type lithium ferric manganese phosphate positive electrode and its preparation method and application |
| CN112885995A (en) * | 2021-04-02 | 2021-06-01 | 河北九丛科技有限公司 | Manufacturing method of lithium ferric manganese phosphate coated high-voltage lithium nickel manganese oxide positive electrode material |
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