CN115893364B - Lithium iron phosphate positive electrode material, and preparation method and application thereof - Google Patents
Lithium iron phosphate positive electrode material, and preparation method and application thereof Download PDFInfo
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- CN115893364B CN115893364B CN202211693100.8A CN202211693100A CN115893364B CN 115893364 B CN115893364 B CN 115893364B CN 202211693100 A CN202211693100 A CN 202211693100A CN 115893364 B CN115893364 B CN 115893364B
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 57
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 18
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 64
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 38
- 239000011574 phosphorus Substances 0.000 claims abstract description 38
- 229910052742 iron Inorganic materials 0.000 claims abstract description 32
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 25
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- 238000010041 electrostatic spinning Methods 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000010405 anode material Substances 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- 239000000835 fiber Substances 0.000 claims abstract description 17
- 229920000049 Carbon (fiber) Polymers 0.000 claims abstract description 15
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000004917 carbon fiber Substances 0.000 claims abstract description 15
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 15
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 14
- 238000004321 preservation Methods 0.000 claims abstract description 9
- 238000009987 spinning Methods 0.000 claims abstract description 9
- 239000000411 inducer Substances 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims abstract description 7
- 238000005245 sintering Methods 0.000 claims abstract description 7
- 238000010000 carbonizing Methods 0.000 claims abstract description 5
- 238000002156 mixing Methods 0.000 claims abstract description 5
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 21
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 12
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 9
- 229960002089 ferrous chloride Drugs 0.000 claims description 7
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 7
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 6
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000003763 carbonization Methods 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 4
- CDVAIHNNWWJFJW-UHFFFAOYSA-N 3,5-diethoxycarbonyl-1,4-dihydrocollidine Chemical compound CCOC(=O)C1=C(C)NC(C)=C(C(=O)OCC)C1C CDVAIHNNWWJFJW-UHFFFAOYSA-N 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- REKWWOFUJAJBCL-UHFFFAOYSA-L dilithium;hydrogen phosphate Chemical compound [Li+].[Li+].OP([O-])([O-])=O REKWWOFUJAJBCL-UHFFFAOYSA-L 0.000 claims description 3
- 229960002413 ferric citrate Drugs 0.000 claims description 3
- 229940062993 ferrous oxalate Drugs 0.000 claims description 3
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 3
- 239000011790 ferrous sulphate Substances 0.000 claims description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 3
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 3
- NPFOYSMITVOQOS-UHFFFAOYSA-K iron(III) citrate Chemical compound [Fe+3].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NPFOYSMITVOQOS-UHFFFAOYSA-K 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- GKQWYZBANWAFMQ-UHFFFAOYSA-M lithium;2-hydroxypropanoate Chemical compound [Li+].CC(O)C([O-])=O GKQWYZBANWAFMQ-UHFFFAOYSA-M 0.000 claims description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 3
- STCOOQWBFONSKY-UHFFFAOYSA-N tributyl phosphate Chemical compound CCCCOP(=O)(OCCCC)OCCCC STCOOQWBFONSKY-UHFFFAOYSA-N 0.000 claims description 3
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 2
- 239000005977 Ethylene Substances 0.000 claims description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 2
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 2
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 2
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 2
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims description 2
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 claims description 2
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 2
- KTWOOEGAPBSYNW-UHFFFAOYSA-N ferrocene Chemical compound [Fe+2].C=1C=C[CH-]C=1.C=1C=C[CH-]C=1 KTWOOEGAPBSYNW-UHFFFAOYSA-N 0.000 claims description 2
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 239000006012 monoammonium phosphate Substances 0.000 claims 1
- 239000010410 layer Substances 0.000 abstract description 7
- 239000002134 carbon nanofiber Substances 0.000 abstract description 5
- 230000009977 dual effect Effects 0.000 abstract description 2
- 239000002344 surface layer Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 14
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 9
- 238000001035 drying Methods 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 238000011056 performance test Methods 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- 239000000376 reactant Substances 0.000 description 4
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000010406 cathode material Substances 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 238000000840 electrochemical analysis Methods 0.000 description 3
- 229910021392 nanocarbon Inorganic materials 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- -1 polytetrafluoroethylene Polymers 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 238000000967 suction filtration Methods 0.000 description 3
- 230000001502 supplementing effect Effects 0.000 description 3
- 239000011149 active material Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000001523 electrospinning Methods 0.000 description 2
- 238000011534 incubation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- WFGBXPXOFAFPTO-UHFFFAOYSA-N [P].[Fe].[Li] Chemical compound [P].[Fe].[Li] WFGBXPXOFAFPTO-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a lithium iron phosphate positive electrode material, a preparation method and application thereof, and relates to the technical field of lithium ion batteries. Specifically, 1) preparing an electrostatic spinning solution containing a phosphorus source or an iron source, carrying out electrostatic spinning to obtain a spinning fiber, and carbonizing to obtain a carbon fiber; 2) Mixing the carbon fiber with a second phosphorus source, a second iron source, a lithium source and a growth inducer for heat preservation reaction to obtain nano array lithium iron phosphate; 3) And sintering the nano-array lithium iron phosphate under the protection of carbon source gas to obtain the lithium iron phosphate anode material. The invention provides a carbon-coated nano lithium iron phosphate array grown on the surface of a carbon nanofiber; through the carbon layers of the surface layer and the basal layer and the lithium iron phosphate array with special microcosmic appearance, the dual enhancement of electronic conduction and ionic conduction is realized, and further, the high low-temperature performance and the high-rate performance are realized, and the method has high performance advantages and application prospects.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium iron phosphate positive electrode material, a preparation method and application thereof.
Background
The lithium ion battery is a new generation green high-energy battery with excellent performance, and has become one of the key points of the development of high-tech technology; common lithium ion battery anode materials comprise lithium cobaltate, lithium manganate, lithium iron phosphate and ternary materials, wherein the lithium iron phosphate is the anode material which is applied to the electric automobile at first, has abundant raw materials and low cost, obtains market acceptance by virtue of the advantages of large capacity, safety, environmental protection, long service life, wide working temperature range and the like, and becomes one of the most widely commercialized lithium ion anode materials at present. However, lithium iron phosphate has a certain defect in low temperature and rate capability because of poor electron conductivity and lithium ion diffusion capability, and is difficult to meet the requirements of low temperature and high rate charge and discharge.
Currently, modification of lithium iron phosphate is mainly focused on bulk doping, carbon cladding, nanocrystallization and surface morphology modification. The invention patent with the application number of CN201810595889.0 discloses a preparation method of a lithium battery composite positive electrode material wrapped by a carbon material, which comprises the following steps: 1) Uniformly mixing a lithium ion battery anode material, a carbon nano tube, an organic carbon source and an organic solvent to prepare a spinning solution, and carrying out electrostatic spinning to prepare a composite precursor; 2) And carbonizing the composite precursor. The active material particles are uniformly distributed in the carbon nanofiber (carbon matrix) obtained by combining electrostatic spinning with carbonization of a subsequent heat treatment process, and the carbon matrix can effectively inhibit the agglomeration and growth problems of material grains in the processes of heat treatment and the like. However, the active material is located inside the carbon layer, which can seriously obstruct the transmission of lithium ions and has low electron conductivity.
In view of this, the present invention has been made.
Disclosure of Invention
The first aim of the invention is to provide a preparation method of a lithium iron phosphate anode material, and to obtain carbon coated nano-array lithium iron phosphate by carbon nanofiber induced growth; in order to achieve the above object of the present invention, the following technical solutions are specifically adopted:
Step one: preparing an electrostatic spinning solution containing a phosphorus source or an iron source, carrying out electrostatic spinning to obtain spinning fibers, and carbonizing the spinning fibers to obtain carbon fibers containing active sites of the phosphorus source or the iron source;
step two: mixing the carbon fiber with a second phosphorus source, a second iron source, a lithium source and a growth inducer for heat preservation reaction to obtain carbon fiber induced growth nano-array lithium iron phosphate;
step three: and sintering the nano-array lithium iron phosphate under the protection of carbon source gas to obtain the lithium iron phosphate anode material.
Preferably, in step one, the phosphorus source comprises at least one of tributyl phosphate, ammonium dihydrogen phosphate or disodium hydrogen phosphate; the iron source comprises at least one of ferrocene, ferric acetylacetonate or ferric citrate.
Preferably, in the step one, the mass ratio of the phosphorus source to the iron source in the electrospinning solution is 2% -10%.
Preferably, the solvent of the electrostatic spinning solution is at least one of polyvinylpyrrolidone, polyacrylonitrile or polyethylene oxide.
Preferably, in the first step, the carbonization temperature is 400 ℃ to 600 ℃.
Preferably, in the second step, the growth inducer includes at least one of ethylene glycol, dimethyl sulfoxide, glycerol, or ethylenediamine; the second phosphorus source comprises at least one of phosphoric acid, lithium hydrogen phosphate or lithium dihydrogen phosphate; the second iron source comprises at least one of ferrous chloride, ferrous oxalate, ferrous nitrate or ferrous sulfate; the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxalate, lithium chloride, or lithium lactate.
Preferably, the phosphorus in the phosphorus source and the second phosphorus source is taken as total phosphorus, the iron in the iron source and the second iron source is taken as total iron, and the molar ratio of lithium, total phosphorus and total iron in the lithium source is (2.8-3.4): (0.9-1): 1.
Preferably, in the second step, the temperature of the heat preservation reaction is 140-240 ℃, and the time of the heat preservation reaction is 1-12 h.
Preferably, in the third step, the sintering temperature is 450 ℃ to 700 ℃.
Preferably, in the third step, the carbon source gas includes at least one of methane, ethane, acetylene, and ethylene.
The second object of the present invention is to provide a lithium iron phosphate positive electrode material prepared by the preparation method of the lithium iron phosphate positive electrode material, which has excellent rate capability and low temperature capability, and can realize high rate discharge.
A third object of the present invention is to provide the use of the lithium iron phosphate positive electrode material in a lithium ion battery; for example, the lithium ion battery anode and the prepared anode piece are prepared by the lithium iron phosphate anode material, the lithium ion battery and the prepared lithium ion battery are prepared by the lithium iron phosphate anode material, the electric appliance and the prepared electric equipment are prepared by the lithium iron phosphate anode material, and the application of the lithium iron phosphate anode material in the lithium ion battery is provided.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a carbon-coated nano lithium iron phosphate array grown on the surface of a carbon nanofiber, wherein the nano lithium iron phosphate array vertically and radially grows on the surface of the carbon nanofiber, and the diameter and the length of the lithium iron phosphate are both nano-scale, so that the diffusion rate of lithium ions can be effectively improved; meanwhile, the carbon fiber serving as the lithium iron phosphate substrate is cooperated with the nano carbon layer deposited on the surface of the lithium iron phosphate, so that the electronic conductivity is effectively improved. The high low-temperature performance and the high-rate performance can be realized under the dual functions of electron conduction and ion conduction.
Detailed Description
The technical solution of the present invention will be clearly and completely described in conjunction with the specific embodiments, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are intended to be illustrative only and should not be construed as limiting the scope of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The invention is implemented by the following specific technical means: step one: preparing an electrostatic spinning solution containing a phosphorus source or an iron source, carrying out electrostatic spinning to obtain spinning fibers, and carbonizing the spinning fibers to obtain carbon fibers containing active sites of the phosphorus source or the iron source; step two: mixing the carbon fiber with a second phosphorus source, a second iron source, a lithium source and a growth inducer for heat preservation reaction to obtain carbon fiber induced growth nano-array lithium iron phosphate; step three: and sintering the nano-array lithium iron phosphate under the protection of carbon source gas to obtain the lithium iron phosphate anode material.
The lithium iron phosphate positive electrode material prepared by the invention mainly comprises carbonized spinning fibers (corresponding to the carbon fibers prepared in the first step) serving as a basal layer, nano-sized array lithium iron phosphate (corresponding to the second step) growing on the carbon fibers, and a nano-carbon layer (corresponding to the carbon coating prepared in the third step) deposited on the surface layer of the lithium iron phosphate after being sintered by carbon source gas.
As a preferred embodiment, the carbon fiber has a diameter of 200nm to 400nm, including but not limited to 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, 400nm; the diameter of the nano-array lithium iron phosphate is 5-10 nm, including but not limited to 5nm, 6nm, 7nm, 8nm, 9nm and 10nm; the length of the nano-array lithium iron phosphate is 50-100 nm, including but not limited to 50nm, 60nm, 70nm, 80nm, 90nm and 100nm; the thickness of the nano carbon layer (or carbon coating layer) is 1 nm-3 nm, including but not limited to 1nm, 1.2nm, 1.4nm, 1.6nm, 1.8nm, 2nm, 2.2nm, 2.4nm, 2.6nm, 2.8nm and 3nm. It should be noted that the parameter values according to the present invention may be any of the real values in the numerical intervals formed by the above-mentioned point values.
In the first step of the present invention, the electrospinning solution may contain only the phosphorus source or only the iron source; but the mass ratio of the phosphorus source or the iron source in the electrostatic spinning solution is ensured to be 2-10%. Correspondingly, the addition amounts of the second phosphorus source and the second iron source in the second step are controlled according to the addition amounts of the phosphorus source or the iron source, so that the molar ratio of all lithium, phosphorus and iron contained in the positive electrode material is satisfied (2.8-3.4): (0.9-1): 1.
As a preferable embodiment, the advancing speed of the electrostatic spinning is 0.005 mL/min-0.1 mL/min, the receiving distance of the electrostatic spinning is 10 cm-20 cm, and the direct-current high voltage of the electrostatic spinning is 6 kV-20 kV.
As a preferred embodiment, in step one, the carbonization temperature includes, but is not limited to, 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃.
As a preferred embodiment, the addition amount of the growth inducer is 5% -25% of the total mass of the reaction system.
As a preferred embodiment, in the second step, the temperature of the incubation reaction includes, but is not limited to, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃, 240 ℃, and the time of the incubation reaction includes, but is not limited to, 1h, 2h, 4h, 6h, 8h, 10h, 12h.
As a preferred embodiment, in step three, the sintering temperature includes, but is not limited to, 450 ℃, 480 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃.
Example 1
1) Polyacrylonitrile and 0.1g tributyl phosphate were dissolved in 20ml of n, n-dimethylformamide and stirred uniformly to prepare a solution with a solid content of 20%. Setting the vertical distance between the electrostatic spinning rotary drum collector and the needle head to be 15cm, setting the direct current voltage at two ends to be 10kV, drying the obtained fiber containing the phosphorus source precursor after a certain time, pre-oxidizing at 200 ℃, and then preserving the heat for 2 hours at 600 ℃ to obtain the carbonized fiber.
2) Adding the fiber obtained in the step 1) into a polytetrafluoroethylene reaction kettle, adding an ethylene glycol aqueous solution with the mass fraction of 10%, and supplementing lithium dihydrogen phosphate, ferrous chloride and lithium hydroxide to ensure that the molar ratio of lithium iron to phosphorus in the reactant is 3:0.96:1, preserving heat at 180 ℃ for reaction for 3 hours; and after the reaction is finished, carrying out suction filtration, and cleaning and drying the obtained solid sample.
3) And 2) taking the dried sample obtained in the step 2), heating to 600 ℃ at 10 ℃/min in a tube furnace in methane atmosphere, and preserving heat for 3 hours to obtain the high-rate lithium iron phosphate anode material.
Example 2
1) Polyacrylonitrile and 0.05g of ferric acetylacetonate are taken and dissolved in 20mL of N, N-dimethylformamide, and the mixture is stirred uniformly to prepare a solution with 15% of solid content. Setting the vertical distance between the electrostatic spinning rotary drum collector and the needle head to be 15cm, setting the direct current voltage at two ends to be 10kV, drying the obtained fiber containing the phosphorus source precursor after a certain time, pre-oxidizing at 200 ℃, and then preserving the heat for 2 hours at 600 ℃ to obtain the carbonized fiber.
2) Adding the fiber obtained in the step 1) into a polytetrafluoroethylene reaction kettle, adding an ethylene glycol aqueous solution with the mass fraction of 20%, and supplementing lithium dihydrogen phosphate, ferrous chloride and lithium hydroxide to ensure that the molar ratio of lithium iron to phosphorus in the reactant is 3.1:0.97:1, carrying out heat preservation reaction for 4 hours at 160 ℃; and after the reaction is finished, carrying out suction filtration, and cleaning and drying the obtained solid sample.
3) And 2) taking the dried sample obtained in the step 2), heating to 650 ℃ at a speed of 5 ℃ per minute in a tube furnace in methane atmosphere, and preserving heat for 2 hours to obtain the high-rate lithium iron phosphate anode material.
Example 3
1) Polyvinylpyrrolidone and 0.1g of ferric citrate are taken and dissolved in 20mL of N, N-dimethylformamide, and the mixture is stirred uniformly to prepare a solution with 15% of solid content. Setting the vertical distance between the electrostatic spinning rotary drum collector and the needle head to be 15cm, setting the direct current voltage at two ends to be 10kV, drying the obtained fiber containing the phosphorus source precursor after a certain time, pre-oxidizing at 220 ℃, and preserving the heat for 2 hours at 600 ℃ to obtain the carbonized fiber.
2) Adding the fiber obtained in the step 1) into a polytetrafluoroethylene reaction kettle, adding a glycerol aqueous solution with the mass fraction of 15%, and supplementing lithium dihydrogen phosphate, ferrous chloride and lithium hydroxide to ensure that the molar ratio of lithium iron to phosphorus in the reactant is 3.3:0.97: the reaction is carried out for 5 hours at the temperature of 1, 140 ℃; and after the reaction is finished, carrying out suction filtration, and cleaning and drying the obtained solid sample.
3) And 2) taking the dried sample obtained in the step 2), heating to 650 ℃ at a speed of 5 ℃ per minute in a tube furnace in methane atmosphere, and preserving heat for 2 hours to obtain the high-rate lithium iron phosphate anode material.
Example 4
Substantially the same as in example 1, the only difference is that: in step 2), the added lithium dihydrogen phosphate, ferrous chloride and lithium hydroxide are replaced by: phosphoric acid, ferrous sulfate and lithium lactate.
Example 5
Substantially the same as in example 1, the only difference is that: in step 2), the added lithium dihydrogen phosphate, ferrous chloride and lithium hydroxide are replaced by: lithium hydrogen phosphate, ferrous oxalate and lithium carbonate.
Example 6
Substantially the same as in example 1, the only difference is that: in step 2), the molar ratio of lithium iron phosphorus in the reactant is 2.8:1:1.
Test examples
(One) button cells were prepared using the high-rate lithium iron phosphate cathode material of example 1 according to the following methods, respectively: and directly cutting and rolling the high-rate lithium iron phosphate anode material, assembling a CR2032 button battery by taking the lithium sheet as a negative electrode, and carrying out electrochemical test on the button battery. The electrochemical performance of the button cell was measured at 2.1V-3.75V, 0.1C/0.1C, 0.2C/0.2C, 0.2C/0.33C, 0.2C/0.5C, 0.2C/1C, and 0.2C/2C rates, and the results are shown in Table 1.
Table 1 performance test table
Second, button cells were prepared from the high-rate lithium iron phosphate cathode materials of examples 1 to 6 in the same manner as above, and electrochemical tests were performed on the series of button cells. The button cell was subjected to electrochemical performance tests at a rate of 2.1V to 3.75V and 0.2C/2C, and the first-cycle charge and discharge results are shown in Table 2.
Table 2 electrochemical performance test table
(III) button cells were prepared from the high-rate lithium iron phosphate cathode materials of examples 1 to 6 in the same manner as above, and electrochemical tests were performed on the series of button cells in an environment of-20 ℃. The button cell was subjected to electrochemical performance test at a voltage range of 2.1V to 3.75V and a rate of 0.1C/0.1C, and the first charge and discharge results are shown in Table 3.
Table 3 electrochemical performance test table
While the invention has been illustrated and described with reference to specific embodiments, it is to be understood that the above embodiments are merely illustrative of the technical aspects of the invention and not restrictive thereof; those of ordinary skill in the art will appreciate that: modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some or all of the technical features thereof, without departing from the spirit and scope of the present invention; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions; it is therefore intended to cover in the appended claims all such alternatives and modifications as fall within the scope of the invention.
Claims (8)
1. The preparation method of the lithium iron phosphate anode material is characterized by comprising the following steps of:
Step one: preparing an electrostatic spinning solution containing a phosphorus source or an iron source, carrying out electrostatic spinning to obtain spinning fibers, and carbonizing the spinning fibers to obtain carbon fibers containing active sites of the phosphorus source or the iron source;
In the electrostatic spinning solution, the mass ratio of the phosphorus source to the iron source is 2% -10%;
step two: mixing the carbon fiber with a second phosphorus source, a second iron source, a lithium source and a growth inducer for heat preservation reaction to obtain carbon fiber induced growth nano-array lithium iron phosphate;
The growth inducer comprises at least one of ethylene glycol, dimethyl sulfoxide, glycerol or ethylenediamine; the temperature of the heat preservation reaction is 140-240 ℃, and the time of the heat preservation reaction is 1-12 h;
Step three: sintering the nano-array lithium iron phosphate under the protection of carbon source gas to obtain a lithium iron phosphate anode material;
the carbon source gas includes at least one of methane, ethane, acetylene, and ethylene; the sintering temperature is 450-700 ℃.
2. The method for producing a lithium iron phosphate positive electrode material according to claim 1, wherein the phosphorus source comprises at least one of tributyl phosphate, monoammonium phosphate, or disodium hydrogen phosphate;
and/or the iron source comprises at least one of ferrocene, ferric acetylacetonate or ferric citrate.
3. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the solvent of the electrostatic spinning solution is at least one of polyvinylpyrrolidone, polyacrylonitrile or polyethylene oxide.
4. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the carbonization temperature is 400 ℃ to 600 ℃.
5. The method for producing a lithium iron phosphate positive electrode material according to claim 1, wherein the second phosphorus source comprises at least one of phosphoric acid, lithium hydrogen phosphate, or lithium dihydrogen phosphate;
And/or, the second iron source comprises at least one of ferrous chloride, ferrous oxalate, ferrous nitrate, or ferrous sulfate;
and/or the lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium oxalate, lithium chloride, or lithium lactate.
6. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein phosphorus in the phosphorus source and the second phosphorus source is taken as total phosphorus, iron in the iron source and the second iron source is taken as total iron, and a molar ratio of lithium, total phosphorus and total iron in the lithium source is (2.8-3.4): (0.9-1): 1.
7. The lithium iron phosphate positive electrode material prepared by the preparation method of the lithium iron phosphate positive electrode material according to any one of claims 1 to 6.
8. Use of the lithium iron phosphate positive electrode material according to claim 7 in a lithium ion battery.
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