CN115180609B - Lithium iron phosphate preparation process suitable for industrialization - Google Patents
Lithium iron phosphate preparation process suitable for industrialization Download PDFInfo
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- CN115180609B CN115180609B CN202210961650.7A CN202210961650A CN115180609B CN 115180609 B CN115180609 B CN 115180609B CN 202210961650 A CN202210961650 A CN 202210961650A CN 115180609 B CN115180609 B CN 115180609B
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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 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 76
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 42
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 28
- 239000002096 quantum dot Substances 0.000 claims abstract description 28
- 238000001354 calcination Methods 0.000 claims abstract description 18
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 17
- 229910052742 iron Inorganic materials 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- 239000002994 raw material Substances 0.000 claims abstract description 13
- 238000000227 grinding Methods 0.000 claims abstract description 11
- 238000000498 ball milling Methods 0.000 claims abstract description 8
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000007873 sieving Methods 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- 239000002245 particle Substances 0.000 claims description 13
- 229930006000 Sucrose Natural products 0.000 claims description 11
- 239000005720 sucrose Substances 0.000 claims description 11
- 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 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical group [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 5
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical group [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- 238000010298 pulverizing process Methods 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000006185 dispersion Substances 0.000 claims description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 3
- 239000005955 Ferric phosphate Substances 0.000 claims description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 2
- 239000006229 carbon black Substances 0.000 claims description 2
- 229940032958 ferric phosphate Drugs 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims description 2
- 239000008103 glucose Substances 0.000 claims description 2
- 125000002791 glucosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)[C@H](O1)CO)* 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 10
- 238000000034 method Methods 0.000 abstract description 7
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 238000002474 experimental method Methods 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 6
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 230000001351 cycling effect Effects 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 3
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 125000005842 heteroatom Chemical group 0.000 description 2
- 229910000398 iron phosphate Inorganic materials 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 241000212749 Zesius chrysomallus Species 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 125000000185 sucrose group Chemical group 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000001291 vacuum drying Methods 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- 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
Abstract
A preparation process of lithium iron phosphate suitable for industrialization belongs to the field of new energy. The method aims to solve the problem that the existing industrialized lithium iron phosphate has poor electrochemical performance. The process comprises the following steps: 1. taking an iron source, a lithium source, a carbon source and a graphene quantum dot material as raw materials, mixing, grinding and dispersing; 2. calcining in a tube furnace under the flow rate atmosphere, ball milling and sieving to obtain the lithium iron phosphate. The invention has simple steps and equipment, and is suitable for mass production. The conductivity of the lithium iron phosphate material is improved by 26% compared with that of the material without the addition. The cycle performance of the assembled battery is increased, the conductivity of the graphene quantum dot material is very excellent, more conductive sites are provided for the battery material, the transmission of electrons during the battery cycle is facilitated, the activity of the reaction is increased, the short plates with poor conductivity of the lithium iron phosphate are improved, the better performance is exerted, and a foundation is laid for the breakthrough of the current commercialized pattern of the lithium iron phosphate. The method is suitable for the industrialized preparation of the lithium iron phosphate.
Description
Technical Field
The invention belongs to the field of new energy sources; in particular to a preparation process of lithium iron phosphate suitable for industrialization.
Background
The upstream of the lithium iron phosphate industrial chain mainly comprises raw materials such as lithium sources, iron sources, carbon sources, phosphate radicals and the like, the midstream comprises lithium iron phosphate anode materials, and the downstream comprises applications such as lithium iron phosphate batteries, new energy automobiles, energy storage and the like. Along with the rapid increase of downstream demand in four seasons in 2020, the supply and demand gap of the lithium iron phosphate material is gradually enlarged, the price of the superimposed upstream lithium carbonate is increased, and the price of the lithium iron phosphate material enters an ascending channel. The price of the 5-month lithium iron phosphate in 2021 is 5 ten thousand yuan one ton, and the price of the 5-month lithium iron phosphate in 2022 is 15 ten thousand yuan one ton.
The existing industrialized lithium iron phosphate has the problem of poor electrochemical performance. Lithium iron also maintains a relatively "high cost performance" in the case of high prices for lithium battery materials. The lithium iron phosphate has the mass capacity between that of the lithium cobalt oxide and that of the ternary material, and the energy density is lower than that of the ternary material, but the lithium iron phosphate has the advantages of stable structure, good cycle performance and good safety performance, and is a positive electrode material with high cost performance. Because the lithium iron phosphate does not contain noble metals such as cobalt, nickel and the like, the price fluctuation of the lithium iron phosphate is far smaller than that of a ternary material, and the cost control is facilitated.
Disclosure of Invention
The invention aims to solve the problem of poor electrochemical performance of the existing industrialized lithium iron phosphate, and provides a preparation process of the lithium iron phosphate suitable for industrialization.
The preparation process of the lithium iron phosphate suitable for industrialization is realized according to the following steps:
1. taking an iron source, a lithium source, a carbon source and a graphene quantum dot material as raw materials, mixing and grinding, and dispersing;
2. and (3) placing the dispersed material into a tube furnace, calcining under the flow rate atmosphere, ball-milling and sieving the calcined product to obtain lithium iron phosphate, namely finishing the preparation of the lithium iron phosphate suitable for industrialization.
According to the invention, in the research process, the optimal proportioning and the calcination temperature for preparing the lithium iron phosphate are described by experimental conditions such as different calcination temperatures and different material proportions, whether a graphene quantum dot material is added or not, and experiments prove that the cycle performance of the lithium iron phosphate added with the graphene quantum dot material is improved by 26% compared with that of a blank group, the first cycle performance is excellent, and the graphene quantum dot material plays a role in conducting communication in the lithium iron phosphate, so that the transmission of electrons and the conduction of ions are promoted. The conductivity of the lithium iron phosphate is improved, the process is low in manufacturing cost and simple in steps, and a new industrialization direction is provided for the improvement of the energy density and the industrialization of the lithium iron phosphate.
The preparation process of the lithium iron phosphate has simple steps, needs simple equipment and is suitable for mass production. The invention takes common iron source, lithium source and carbon source as raw materials, and adds graphene quantum dot material, so that the conductivity of the lithium iron phosphate material is improved by 26% compared with that of the material without addition. The assembled battery shows that the circulation performance of the material is improved, because the graphene quantum dot material is excellent in conductivity, more conductive sites are provided for the battery material, the transmission of electrons during the battery circulation is facilitated, the reaction activity is increased, the natural short plate-poor conductivity of the lithium iron phosphate is improved, the circulation performance of the material is enhanced, the market of the power battery can be continuously led to with high performance, and a foundation is laid for the breakthrough of the current commercialized pattern of the lithium iron phosphate.
The method is suitable for the industrialized preparation of the lithium iron phosphate.
Drawings
FIG. 1 is an XRD pattern of a blank set of lithium iron phosphate prepared in example 1;
FIG. 2 is an SEM image of blank lithium iron phosphate prepared in example 1;
FIG. 3 is a battery cycle diagram of a Blank set of lithium iron phosphate prepared in example 1, wherein ■ represents LFP Blank;
FIG. 4 is an XRD pattern of lithium iron phosphate prepared in example 3;
FIG. 5 is an SEM image of lithium iron phosphate prepared according to example 3;
FIG. 6 is a battery cycle diagram of lithium iron phosphate prepared in example 3, wherein ■ represents LFP at 740 ℃;
FIG. 7 is an XRD pattern of modified lithium iron phosphate prepared in example 7;
FIG. 8 is an SEM image of the modified lithium iron phosphate prepared according to example 7;
FIG. 9 is a battery cycle diagram of the modified lithium iron phosphate prepared in example 7, wherein ■ represents C-LFP;
fig. 10 is a battery cycle diagram of the lithium iron phosphate prepared in example 1 and the modified group of lithium iron phosphates prepared in example 7, wherein ■ represents C-LFP, +..
Detailed Description
The technical scheme of the invention is not limited to the specific embodiments listed below, and also includes any combination of the specific embodiments.
The first embodiment is as follows: the preparation process of the lithium iron phosphate suitable for industrialization is realized according to the following steps:
1. taking an iron source, a lithium source, a carbon source and a graphene quantum dot material as raw materials, and carrying out mixing, grinding and dispersing;
2. and (3) placing the dispersed material into a tube furnace, calcining under the flow rate atmosphere, ball-milling and sieving the calcined product to obtain lithium iron phosphate, namely finishing the preparation of the lithium iron phosphate suitable for industrialization.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is that the molar ratio of the iron source, the lithium source and the carbon source in the first step is 1 (1-1.1): 0.09-0.2. Other steps and parameters are the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from the first or second embodiments in that the iron source in the first step is iron phosphate. Other steps and parameters are the same as in the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one to three embodiments in that the lithium source in step one is lithium hydroxide, lithium carbonate, or lithium chloride. Other steps and parameters are the same as in one to three embodiments.
Fifth embodiment: this embodiment differs from one to four embodiments in that the carbon source in step one is glucose, sucrose, or carbon black. Other steps and parameters are the same as in one to four embodiments.
Specific embodiment six: the difference between the embodiment and the embodiment is that the dosage of the graphene quantum dot material in the step one is 1 per mill to 10 percent of the total mass of the raw materials. Other steps and parameters are the same as in one of the first to fifth embodiments.
Seventh embodiment: the present embodiment is different from one to six of the embodiments in that the particle diameter of the graphene quantum dot in the first step is 5nm. Other steps and parameters are the same as in one of the first to sixth embodiments.
In this embodiment, the graphene quantum dot material is a commercial product, and is purchased from Guangzhou cis-state energy science and technology limited company.
Eighth embodiment: this embodiment differs from one of the first to seventh embodiments in that the grinding dispersion is described in the first step: pulverizing and dispersing for 5min by adopting a grinding machine with the power of 550W. Other steps and parameters are the same as those of one of the first to seventh embodiments.
In this embodiment, the particle size after pulverizing and dispersing is 500 mesh.
Detailed description nine: this embodiment differs from one of the first to eighth embodiments in that the calcination is performed under the flow rate atmosphere in the second step: the temperature rising rate is 2-8 ℃/min, the temperature is controlled to be 600-740 ℃, the heat preservation time is 200-700 min, the flow rate is 0.01-0.1L/min, and the atmosphere is nitrogen, argon or argon-hydrogen mixed gas. Other steps and parameters are the same as in one to eight of the embodiments.
Detailed description ten: the difference between the embodiment and one of the specific embodiments from one to nine is that the rotation speed of the ball milling in the second step is 400rpm, the time is 30min, and the ball mass ratio is 1:3; the mesh number of the sieving is 100-500 meshes. Other steps and parameters are the same as in one of the first to ninth embodiments.
The beneficial effects of the invention are verified by the following examples:
unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains; the reagents, medicines, and methods used in the examples below were all of conventional analytical purity, and the experimental methods were all of conventional methods.
Example 1 (blank):
1. taking an iron source, a lithium source and a carbon source as raw materials, and carrying out mixing, grinding and dispersing;
2. and placing the dispersed material into a tube furnace, calcining under the flow rate atmosphere, ball-milling and sieving the calcined product to obtain the lithium iron phosphate.
In the first embodiment, the molar ratio of the iron source, the lithium source and the carbon source is 1:1.1:0.1.
In the first embodiment, the iron source is iron phosphate.
In the first embodiment, the lithium source is lithium carbonate.
In the first embodiment, the carbon source is sucrose.
In the first embodiment, the particle diameter of the graphene quantum dot is 5nm.
The grinding dispersion in step one of this example was as follows: pulverizing and dispersing for 5min by adopting a grinding machine with the power of 550W.
Calcining under the flow rate atmosphere in the second step of the embodiment: the temperature rising rate is 5 ℃/min, the temperature is controlled to be 700 ℃, the heat preservation time is 480min, the flow rate is 0.1L/min, and the atmosphere is argon.
In the second step of the embodiment, the rotation speed of the ball milling is 400rpm, the time is 30min, and the ball mass ratio is 1:3; the mesh number of the sieve is 200 meshes.
The lithium iron phosphate prepared in this example was slurried: mixing lithium iron phosphate, super P and PVDF solution according to a mass ratio of 8:1:1, wherein the concentration of the PVDF solution is 4%, and the solvent of the PVDF solution is N-methylpyrrolidone; coating the pole piece by a 300 mu m scraper after size mixing, vacuum drying the battery pole piece at 100 ℃ for more than 8 hours, cutting the battery pole piece into pole pieces with the diameter of 14mm, and finally assembling the pole pieces into a 2032 half battery, wherein the electrolyte is 1mol LiPF 6 EC DMC emc=1:1:1 wt% performance tests were performed.
Test results: from the XRD pattern of fig. 1, it can be seen that the peaks of lithium iron phosphate substantially correspond to standard colorimetric cards, with the main peaks centered at 20.66 °,25.48 °,29.67 °,35.49 °, which can be indicative of the synthesis of lithium iron phosphate materials. But the hetero peaks shown at 52.49 ℃and 61.64 ℃are mainly Li 3 PO 4 The purity of the sample is not high enough.
As can be seen from the SEM image of fig. 2, the lithium iron phosphate has a small size, the individual particles are nano-sized, and the secondary agglomerated particles are micro-sized, which is advantageous for electrochemical performance. However, particles with insufficient crystallinity are attached to the surface of the lithium iron phosphate, which affects the electrochemical performance.
As can be seen from the battery cycle chart of fig. 3, the effect of cycling 550 times at a current of 1C, the specific capacity of the first-cycle discharge was about 114.11mAh/g, the capacity after cycling 550 cycles was 77.5mAh/g, the capacity retention rate was 68%, and the effect was general.
Example 2 (comparative experiment):
the difference compared to example 1 is that the calcination temperature is reduced from 700 ℃ to 650 ℃.
The battery of example 2 was similar to the blank at low rate (e.g., 0.1C), but the capacity fade was fast at high rate (e.g., 1C).
Example 3 (comparative experiment):
the difference compared to example 1 is that the calcination temperature is increased from 700 to 740 ℃.
The battery of example 3 was subjected to performance testing.
Test results: from the XRD pattern of FIG. 4, it is seen that the peaks of lithium iron phosphate substantially correspond to those of the blank group of lithium iron phosphate, but that the hetero peaks Li 3 PO 4 More obviously, the high temperature is favorable for the crystal form of the material, but the impurities of the material are increased, so that the electrochemical performance of the material is affected.
It can be seen from the SEM image of fig. 5 that the high temperature of lithium iron phosphate does result in a relatively complete crystallization of the material, in which the lithium iron material is essentially olivine, but the size is in the micrometer scale, and the particles of the material are too large to facilitate the deintercalation of lithium ions, thereby affecting the electrochemical performance.
As can be seen from the cycle chart of fig. 6, the effect of cycling for 200 times under the current of 1C has a specific capacity of 109.69mAh/g in the first cycle, a capacity of 91.17mAh/g after cycling for 200 cycles, a capacity retention rate of 83%, and cycle performance consistent with the result of SEM chart, and the material has significant cycle effect under high current due to the increase of particles of high-temperature sintered material, and the capacity retention rate in the cycle is low.
Example 4 (comparative experiment):
the difference compared to example 1 is that the molar ratio of iron source to lithium source is reduced to 1:1.05; the calcination temperature was increased from 700 to 740 ℃.
The battery of example 4 was subjected to performance test.
Example 5 (comparative experiment):
the difference compared to example 1 is that the molar ratio of sucrose is reduced from 0.1 to 0.08; the calcination temperature was increased from 700 to 740 ℃.
The color of the material in example 5 was varied, possibly with insufficient sucrose content, resulting in insufficient amounts of reducing agent during the reaction.
Example 6 (comparative experiment):
the difference compared to example 1 is that the molar ratio of sucrose is from 0.1 to 0.12; the calcination temperature was increased from 700 to 740 ℃.
The material in example 6 was black in color and may have too much sucrose content, resulting in a reduced active mass of the material and poor battery performance.
Example 7 (modified group):
the difference compared with example 1 is that graphene quantum dot material is added; the dosage of the graphene quantum dot material is 1% of the total mass of the raw materials; the particle diameter of the graphene quantum dot material dots is 5nm, and the graphene quantum dot material dots are purchased from Guangzhou cis-state energy science and technology Co.
The peaks of lithium iron phosphate obtained in example 7 are substantially identical to those of fig. 1, indicating that the addition of graphene quantum dot material has no effect on the crystal lattice of lithium iron phosphate. It is noted, however, that the peak intensity increases as seen in the XRD pattern of fig. 7, so that the addition of this material favors crystallization of the material during calcination.
As can be seen from the SEM image of fig. 8, the crystallinity of the particles of lithium iron phosphate is very clear and complete, and the size is smaller than that of fig. 5, and the particles are basically on the nanometer scale, which is more favorable for the deintercalation of lithium ions.
As can be seen from the battery cycle diagrams in fig. 9 and 10, the specific capacity of the first cycle is about 115.3mAh/g under the 1C current cycle, which is consistent with that of the blank group lithium iron phosphate, so that the specific capacity of the first cycle is not affected by adding the graphene quantum dots, but the capacity remaining after 550 cycles is 98.22mAh/g, the capacity retention rate is 85.2%, which is improved by about 26% compared with that of the blank group, and the graphene quantum dots play a positive role in the battery cycle and can be shown ungluingly even under high current. Finally, as can be more clearly seen from fig. 10, the two groups of batteries have little difference in the previous cycle, but the modified lithium iron is obviously more stable under a large current, and the blank group starts to be unstable after 400 circles, the capacity starts to decrease dramatically, but the lithium iron phosphate of the graphene quantum dot can still maintain relative stability, and the added material is proved to be truly effective.
Example 1 is a blank group, and takes ferric phosphate, lithium carbonate and sucrose as raw materials, and the raw materials are dried and ground, placed in a tube furnace and calcined at 700 ℃ for 8 hours to prepare the lithium iron phosphate material. Example 2 to investigate the effect of temperature on lithium iron phosphate, the calcination temperature was reduced from 700 ℃ to 650 ℃ while maintaining the same other experimental conditions. The results show that the quality of the product lithium iron phosphate is reduced, and the cycle performance of the battery is poor under high current. In example 3, the calcining temperature is increased to 740 ℃, the material has obvious cyclic effect under high current because of the increase of particles of the high-temperature sintering material, the capacity of the first circle is lower, and the capacity retention rate in the cycle is lower.
Example 4 shows that the color of the sintered material is brown, the lithium content is reduced, the side reaction is increased, and the purity of the material is not high. In example 5, the molar ratio of sucrose was reduced from 0.1 to 0.08, and the color of the sintered material was deviated, and red spots were formed, which may be the occurrence of iron oxide due to insufficient reducing agent. Example 6 was an increase in sucrose molar ratio to 0.12 with a black material color and a normal lithium iron phosphate material with a gray black color. It is inferred that too much sucrose content results in a decrease in the active mass of the subsequent material, and that the battery performance is poor.
In the embodiment 7, the influence of the graphene quantum dot material on the lithium iron phosphate is compared, firstly, the color of the lithium iron phosphate is gray black, and the XRD also proves that the doped material has no influence on the peak crystal form of the doped material, and the material is assembled by the material, so that the cycle performance of the material is improved, the graphene quantum dot carbon material has excellent conductivity, conductive sites can be provided in a dispersed manner in the material, and the electron transmission during the battery cycle is facilitated. Therefore, the addition of the graphene quantum dot material is favorable for exerting better performance of the lithium iron phosphate, and lays a foundation for the breakthrough of the current commercialized pattern of the lithium iron phosphate.
In summary, the invention discloses a preparation process of lithium iron phosphate suitable for industrialization, which takes a common iron source, a lithium source and a carbon source as raw materials, and a graphene quantum dot material is added, so that the conductivity of the lithium iron phosphate material is improved by 26% compared with that of a material without the graphene quantum dot material. Because the graphene quantum dot material is favorable for improving the poor conductivity of a natural short plate of lithium iron phosphate, the graphene quantum dot material provides more conductive sites for the battery material and increases the activity of the reaction.
So far, those skilled in the art will recognize that while embodiments of the present invention have been shown and described in detail herein, many other variations or modifications of the principles of the present invention can be determined or inferred directly from the disclosure without departing from the spirit and scope of the present invention. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.
Claims (3)
1. The preparation process of the lithium iron phosphate suitable for industrialization is characterized by comprising the following steps of:
1. taking an iron source, a lithium source, a carbon source and a graphene quantum dot material as raw materials, and carrying out mixing, grinding and dispersing;
2. placing the dispersed material into a tube furnace, calcining under the flow rate atmosphere, ball-milling and sieving the calcined product to obtain lithium iron phosphate, namely finishing the preparation of the lithium iron phosphate suitable for industrialization;
wherein the molar ratio of the iron source, the lithium source and the carbon source is 1:1.1:0.1;
the iron source is ferric phosphate;
the lithium source is lithium hydroxide, lithium carbonate or lithium chloride;
the carbon source is glucose, sucrose or carbon black;
the dosage of the graphene quantum dot material is 1% of the total mass of the raw materials;
the particle diameter of the graphene quantum dots is 5 nm;
calcining under the flow rate atmosphere: the temperature rising rate is 2-8 ℃/min, the temperature is controlled to be 700 ℃, the heat preservation time is 200-700 min, the flow rate is 0.01-0.1L/min, and the atmosphere is nitrogen, argon or argon-hydrogen mixed gas.
2. The process for preparing lithium iron phosphate suitable for industrialization according to claim 1, wherein in the first step, the grinding dispersion: pulverizing and dispersing for 5min by adopting a grinding machine with the power of 550W.
3. The process for preparing lithium iron phosphate suitable for industrialization according to claim 1, wherein the rotation speed of the ball milling in the second step is 400rpm, the time is 30min, and the ball mass ratio is 1:3; the mesh number of the sieving is 100-500 meshes.
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