CN105244500A - Preparation method and application of a b-axis LiFePO4/C nanosheet material - Google Patents
Preparation method and application of a b-axis LiFePO4/C nanosheet material Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 46
- 239000002135 nanosheet Substances 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 229910000901 LiFePO4/C Inorganic materials 0.000 title 1
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 72
- 229910010707 LiFePO 4 Inorganic materials 0.000 claims abstract description 53
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims abstract description 28
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000013078 crystal Substances 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 17
- 150000002505 iron Chemical class 0.000 claims abstract description 16
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 15
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 15
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 15
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 14
- 229960005070 ascorbic acid Drugs 0.000 claims abstract description 14
- 235000010323 ascorbic acid Nutrition 0.000 claims abstract description 14
- 239000011668 ascorbic acid Substances 0.000 claims abstract description 14
- 238000003756 stirring Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000008367 deionised water Substances 0.000 claims abstract description 10
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 10
- 239000000243 solution Substances 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000004729 solvothermal method Methods 0.000 claims abstract description 8
- 239000002243 precursor Substances 0.000 claims abstract description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 5
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 claims abstract description 5
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 claims abstract description 5
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 5
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 claims abstract description 5
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 claims abstract description 5
- 239000011259 mixed solution Substances 0.000 claims abstract description 4
- 229960002089 ferrous chloride Drugs 0.000 claims abstract description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims abstract description 3
- 229940006114 lithium hydroxide anhydrous Drugs 0.000 claims abstract description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 29
- 229910001416 lithium ion Inorganic materials 0.000 claims description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 28
- 239000007772 electrode material Substances 0.000 claims description 11
- 239000006230 acetylene black Substances 0.000 claims description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 8
- 239000007774 positive electrode material Substances 0.000 claims description 8
- 239000002033 PVDF binder Substances 0.000 claims description 7
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 7
- 238000011049 filling Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 4
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 239000012295 chemical reaction liquid Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 229910010710 LiFePO Inorganic materials 0.000 claims 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims 1
- 239000005977 Ethylene Substances 0.000 claims 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims 1
- 239000010406 cathode material Substances 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 abstract description 26
- 238000005303 weighing Methods 0.000 abstract description 2
- 238000002156 mixing Methods 0.000 abstract 1
- 150000003839 salts Chemical class 0.000 abstract 1
- 239000011248 coating agent Substances 0.000 description 21
- 238000000576 coating method Methods 0.000 description 21
- 229910052799 carbon Inorganic materials 0.000 description 20
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 18
- 239000002245 particle Substances 0.000 description 14
- 238000009792 diffusion process Methods 0.000 description 11
- 238000002484 cyclic voltammetry Methods 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- -1 polytetrafluoroethylene Polymers 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- 239000000843 powder Substances 0.000 description 6
- 238000009830 intercalation Methods 0.000 description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 description 4
- 239000004743 Polypropylene Substances 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000002687 intercalation Effects 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 239000012074 organic phase Substances 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229920001155 polypropylene Polymers 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000000376 reactant Substances 0.000 description 3
- 238000001291 vacuum drying Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
本发明一种b轴向LiFePO4/C纳米片状材料的制备方法，称取铁盐、磷酸、锂盐、乙二醇及抗坏血酸，将铁盐、磷酸、锂盐、乙二醇及抗坏血酸混合后搅拌30~60分钟，将整个混合溶液移入高压反应釜中进行溶剂热反应，得反应液；其中，所述的铁盐为七水硫酸亚铁或氯化亚铁中的任意一种；锂盐为一水氢氧化锂或无水氢氧化锂中的任意一种；将所得的反应液用去离子水和无水乙醇分别洗涤后烘干，得粉末状混合前驱体，烘干温度控制为60~90℃；将所得的粉末状混合前驱体热处理2~4小时，即得一种b轴向LiFePO4/C纳米片状材料。所得的LiFePO4/C纳米材料，片状颗粒厚度大约为30nm，晶面取向为（010）晶面。
The preparation method of a b-axial LiFePO 4 /C nanosheet material of the present invention comprises weighing iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid, and mixing the iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid After stirring for 30 to 60 minutes, the whole mixed solution is moved into an autoclave for solvothermal reaction to obtain a reaction solution; wherein, the iron salt is any one of ferrous sulfate heptahydrate or ferrous chloride; lithium The salt is any one of lithium hydroxide monohydrate or lithium hydroxide anhydrous; the obtained reaction solution is washed with deionized water and absolute ethanol respectively, and then dried to obtain a powdery mixed precursor, and the drying temperature is controlled as 60-90°C; Heat treatment of the obtained powdery mixed precursor for 2-4 hours to obtain a b-axis LiFePO 4 /C nanosheet material. The thickness of the obtained LiFePO 4 /C nanometer material is about 30 nm, and the crystal plane orientation is (010) crystal plane.
Description
技术领域 technical field
本发明属于电学领域，尤其涉及一种充电电池材料，具体来说是一种b轴向LiFePO4/C纳米片状材料及其制备方法和应用。 The invention belongs to the field of electricity, and in particular relates to a rechargeable battery material, specifically a b-axis LiFePO 4 /C nano sheet material and its preparation method and application.
背景技术 Background technique
大功率锂离子充电电池因为在混合动力汽车和纯电动汽车上的应用而引起世界的极大关注。橄榄石型结构的磷酸铁锂材料被认为是下一代大型高倍率锂离子电池中最具潜力的正极材料之一。它的优点是化学稳定性和热稳定强，理论容量高等。目前，磷酸铁锂的缺点主要是较低的电子电导率和锂离子扩散速率，这就限制了材料的快速充放电性能。对于后面一个缺点，控制LiFePO4颗粒的大小和形貌都是十分必要的，因为Li+在LiFePO4中的扩散只沿着[010]方向。因此缩短锂离子的扩散路径例如合成b轴短的颗粒是提高锂离子扩散速率的有效途径。 High-power lithium-ion rechargeable batteries have attracted great attention in the world because of their application in hybrid electric vehicles and pure electric vehicles. The lithium iron phosphate material with olivine structure is considered to be one of the most potential positive electrode materials in the next generation of large-scale high-rate lithium-ion batteries. Its advantages are strong chemical stability and thermal stability, and high theoretical capacity. At present, the disadvantages of lithium iron phosphate are mainly low electronic conductivity and lithium ion diffusion rate, which limit the rapid charge and discharge performance of the material. For the latter disadvantage, it is necessary to control both the size and morphology of LiFePO 4 particles, since the diffusion of Li + in LiFePO 4 is only along the [010] direction. Therefore, shortening the diffusion path of lithium ions, such as synthesizing particles with short b-axis, is an effective way to increase the diffusion rate of lithium ions.
尽管磷酸铁锂有机相锂离子电池早已进入实际应用阶段，它仍然有些方面需要改善，例如严重的安全问题，经济性和环保性问题。锂离子电池中应用的可燃有机电解质在过充或短路条件下可能会冒烟或燃烧，而且锂离子电池组装环境要求比较苛刻，有机相电解质比较昂贵等原因造成锂离子电池相对比较昂贵。鉴于有机相锂离子电池的以上缺点，人们做了相关的研究来优化电池的技术特性，并开发一种新型的廉价的绿色电池***，将不同的层间化合物引入到水相电池中进行了研究和开发。 Although lithium iron phosphate organic phase lithium-ion batteries have already entered the stage of practical application, it still has some aspects to be improved, such as serious safety issues, economical and environmental issues. The combustible organic electrolytes used in lithium-ion batteries may smoke or burn under overcharge or short-circuit conditions, and the lithium-ion battery assembly environment requirements are relatively harsh, and the organic phase electrolyte is relatively expensive. Lithium-ion batteries are relatively expensive. In view of the above shortcomings of the organic phase lithium-ion battery, people have done related research to optimize the technical characteristics of the battery and develop a new type of cheap green battery system, introducing different interlayer compounds into the aqueous phase battery for research and development.
发明内容 Contents of the invention
针对现有技术中的上述技术问题，本发明提供了一种b轴向LiFePO4/C纳米片状材料及其制备方法和应用，所述的这种b轴向LiFePO4/C纳米片状材料及其制备方法和应用解决了现有技术中的锂电池倍率性能不佳的技术问题。 Aiming at the above-mentioned technical problems in the prior art, the present invention provides a b-axis LiFePO 4 /C nanosheet material and its preparation method and application. The b-axis LiFePO 4 /C nanosheet material The preparation method and application thereof solve the technical problem of poor rate performance of lithium batteries in the prior art.
本发明一种b轴向LiFePO4/C纳米片状材料的制备方法，其特征在于包括以下步骤： A method for preparing a b-axis LiFePO 4 /C nanosheet material of the present invention is characterized in that it comprises the following steps:
（1）、称取铁盐、磷酸、锂盐、乙二醇及抗坏血酸，铁盐、磷酸、锂盐、乙二醇及抗坏血酸的摩尔比为1:1.3~2.0:2.7~3:1.43~2.86：0.05~0.10；将铁盐、磷酸、锂盐、乙二醇及抗坏血酸混合后搅拌30~60分钟，将整个混合溶液移入高压反应釜中进行溶剂热反应，控制溶剂热反应温度为150~200℃，时间为5~20小时，得反应液；其中，所述的铁盐为七水硫酸亚铁或氯化亚铁中的任意一种；锂盐为一水氢氧化锂或无水氢氧化锂中的任意一种； (1) Weigh iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid, and the molar ratio of iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid is 1:1.3~2.0:2.7~3:1.43~2.86 : 0.05~0.10; Mix iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid and stir for 30~60 minutes, move the whole mixed solution into an autoclave for solvothermal reaction, and control the solvothermal reaction temperature to 150~200 ℃, the time is 5 to 20 hours, to obtain a reaction solution; wherein, the iron salt is any one of ferrous sulfate heptahydrate or ferrous chloride; the lithium salt is lithium hydroxide monohydrate or anhydrous hydroxide any of lithium;
（2）、将步骤（1）所得的反应液用去离子水和无水乙醇分别洗涤1~5次后烘干，得粉末状混合前驱体，烘干温度控制为60~90℃； (2) Wash the reaction solution obtained in step (1) with deionized water and absolute ethanol for 1 to 5 times, and then dry to obtain a powdery mixed precursor. The drying temperature is controlled at 60 to 90°C;
（3）、将步骤（2）所得的粉末状混合前驱体在温度为500~700℃条件下热处理2~4小时，即得一种b轴向LiFePO4/C纳米片状材料。 (3) heat-treat the powdery mixed precursor obtained in step (2) at a temperature of 500-700° C. for 2-4 hours to obtain a b-axis LiFePO 4 /C nanosheet material.
进一步的，所述的铁盐为七水硫酸亚铁，锂盐为一水氢氧化锂。 Further, the iron salt is ferrous sulfate heptahydrate, and the lithium salt is lithium hydroxide monohydrate.
进一步的，所述的铁盐、磷酸、锂盐、乙二醇及抗坏血酸的摩尔比为1:1.5:2.7:2.32：0.08；高压反应釜的填装度为60~80%；烘干温度控制为70~80℃。 Further, the molar ratio of the iron salt, phosphoric acid, lithium salt, ethylene glycol and ascorbic acid is 1:1.5:2.7:2.32:0.08; the filling degree of the autoclave is 60-80%; the drying temperature is controlled It is 70~80℃.
进一步的，步骤2）中，用去离子水洗涤时，反应液：去离子水的体积比为1：40~80，用无水乙醇洗涤时，反应液：无水乙醇的体积比为1：1~3。 Further, in step 2), when washing with deionized water, the volume ratio of reaction liquid: deionized water is 1:40~80, and when washing with absolute ethanol, the volume ratio of reaction liquid: absolute ethanol is 1: 1~3.
本发明还提供了通过上述的制备方法所得的一种b轴向LiFePO4/C纳米片状材料，所述的b轴向LiFePO4/C纳米片状材料晶粒厚度为28~37nm，晶面取向为（010）晶面。 The present invention also provides a b-axis LiFePO 4 /C nano-sheet material obtained by the above-mentioned preparation method. The grain thickness of the b-axis LiFePO 4 /C nano-sheet material is 28-37 nm, and the crystal plane The orientation is (010) crystal plane.
本发明还提供了上述的LiFePO4/C纳米片状材料在制备可充锂离子电池的正极材料中的用途。 The present invention also provides the use of the above-mentioned LiFePO 4 /C nanosheet material in the preparation of positive electrode materials for rechargeable lithium ion batteries.
本发明还提供了上述的可充锂离子电池的正极材料的制备方法，按质量比称取LiFePO4/C电极材料、乙炔黑、聚偏二氟乙烯，LiFePO4/C电极材料、乙炔黑、聚偏二氟乙烯的质量比为80：10：10，将电极材料、乙炔黑和聚偏二氟乙烯混合均匀并溶于N-甲基吡咯烷酮中，涂在处理过的铂电极上，烘干，即得可充锂离子电池的正极材料。 The present invention also provides the preparation method of the positive electrode material of the above-mentioned rechargeable lithium-ion battery, by weighing LiFePO 4 /C electrode material, acetylene black, polyvinylidene fluoride, LiFePO 4 /C electrode material, acetylene black, The mass ratio of polyvinylidene fluoride is 80:10:10, the electrode material, acetylene black and polyvinylidene fluoride are mixed evenly and dissolved in N-methylpyrrolidone, coated on the treated platinum electrode, and dried , that is, a positive electrode material that can be charged with a lithium-ion battery.
本发明用乙二醇作溶剂，将化学计量比铁盐、磷酸、锂盐、乙二醇及一定量的抗坏血酸混合，将整个混合溶液移入内衬聚四氟乙烯的高压反应釜中进行溶剂热反应，洗涤并烘干得粉末状混合前驱体，再将其在N2气氛保护下中热处理，最终得一种b轴短的片状LiFePO4/C纳米材料。所得的LiFePO4/C纳米材料，片状颗粒厚度大约为30nm左右，晶面取向为（010）晶面，即b轴短的片状颗粒。该纳米材料具有较好的电化学行为，用于可充锂离子电池的正极。由于锂离子在磷酸铁锂中的扩散只沿着[010]方向，因此合成b轴短的片状颗粒能缩短锂离子的扩散路径，提高锂离子的扩散系数，从而增强磷酸铁锂的倍率性能。 The present invention uses ethylene glycol as a solvent, mixes stoichiometric iron salt, phosphoric acid, lithium salt, ethylene glycol and a certain amount of ascorbic acid, and moves the whole mixed solution into a high-pressure reactor lined with polytetrafluoroethylene for solvent heating. Reaction, washing and drying to obtain a powdery mixed precursor, and then heat-treating it under the protection of N 2 atmosphere, finally obtaining a sheet-like LiFePO 4 /C nanomaterial with a short b-axis. The thickness of the obtained LiFePO 4 /C nanomaterials is about 30 nm, and the crystal plane orientation is (010), that is, the flake particles with short b-axis. The nanomaterial has good electrochemical behavior and is used as the positive electrode of a rechargeable lithium-ion battery. Since the diffusion of lithium ions in lithium iron phosphate is only along the [010] direction, the synthesis of sheet-like particles with short b-axis can shorten the diffusion path of lithium ions and increase the diffusion coefficient of lithium ions, thereby enhancing the rate performance of lithium iron phosphate .
为了测试样品的电化学性能，对实施例1~3所制备的LiFePO4/C电极材料进行了循环伏安测试。循环伏安测试探究了扫描速率大小对样品在硫酸锂水溶液中发生的氧化还原行为的影响。扫描速率从50mV/s开始增大到280mV/s，曲线仍能出现明显的氧化还原峰，且峰值电压和电流呈现规律性的增加，这表明样品在大扫数下即快速充放电条件下仍能进行锂离子的脱/嵌电化学行为，体现了较好的电化学稳定性和循环寿命。 In order to test the electrochemical performance of the samples, cyclic voltammetry tests were carried out on the LiFePO 4 /C electrode materials prepared in Examples 1-3. The cyclic voltammetry test explored the influence of the scan rate on the redox behavior of the sample in lithium sulfate aqueous solution. When the scan rate increases from 50mV/s to 280mV/s, the curve can still show obvious redox peaks, and the peak voltage and current increase regularly, which shows that the sample is still stable under the condition of large scan number, that is, fast charge and discharge. It can carry out the de/intercalation electrochemical behavior of lithium ions, which reflects good electrochemical stability and cycle life.
本发明采用溶剂热法制备b轴向LiFePO4/C纳米片状材料。溶剂热法被证明是一种有效控制尺寸合成LiFePO4晶体的方法。乙二醇是溶剂热法合成磷酸铁锂材料最常用的一种有机溶剂，具有一定的还原能力，能保证Fe2+不被空气中的氧气氧化。乙二醇作为多羟基的醇，能够诱导纳米粒子生长成纳米片。乙二醇又由于具有适当的粘度，能够很容易的通过羟基和氧原子之间的氢键吸附到（010）晶面上，能够造成了颗粒的独特的晶体取向。同时，醇分子的吸附作用又抑制了磷酸铁锂颗粒的长大。b轴向LiFePO4/C纳米片状材料作为锂离子电池正极材料，b轴向（010）晶面片状的磷酸铁锂由于具有较短的锂离子扩散路径，因此合成的磷酸铁锂具有优异的倍率性能，在动力电池领域具有广阔的应用潜力。该实验过程操作简便，条件易于控制，并且在热处理过程中完成包碳，简化了操作流程，便于工业化大规模生产。 The invention adopts a solvothermal method to prepare the b-axis LiFePO 4 /C nanosheet material. The solvothermal method was proved to be an effective method for the size - controlled synthesis of LiFePO4 crystals. Ethylene glycol is the most commonly used organic solvent for solvothermal synthesis of lithium iron phosphate materials. It has a certain reducing ability and can ensure that Fe 2+ is not oxidized by oxygen in the air. Ethylene glycol, as a polyhydric alcohol, can induce the growth of nanoparticles into nanosheets. Due to its proper viscosity, ethylene glycol can easily adsorb to the (010) crystal plane through the hydrogen bond between hydroxyl and oxygen atoms, which can cause the unique crystal orientation of the particles. At the same time, the adsorption of alcohol molecules inhibits the growth of lithium iron phosphate particles. The b-axis LiFePO 4 /C nanosheet material is used as the positive electrode material of lithium-ion batteries, and the b-axis (010) crystal facet-shaped lithium iron phosphate has a short lithium ion diffusion path, so the synthesized lithium iron phosphate has excellent The rate performance has a broad application potential in the field of power batteries. The experimental process is easy to operate, the conditions are easy to control, and the carbon encapsulation is completed in the heat treatment process, which simplifies the operation process and is convenient for large-scale industrial production.
本发明和已有技术相比，其技术进步是显著的。通过本发明的方法获得的b轴向LiFePO4/C纳米片状材料晶粒尺寸均匀、具有更好脱/嵌锂能力、是一种低成本的锂离子电池正极材料。 Compared with the prior art, the technical progress of the present invention is remarkable. The b-axis LiFePO 4 /C nano sheet material obtained by the method of the invention has uniform crystal grain size, better lithium extraction/intercalation ability, and is a low-cost lithium ion battery positive electrode material.
附图说明 Description of drawings
图1是实施例1、2、3碳包覆热处理前所得的LiFePO4材料的XRD图谱。 Fig. 1 is the XRD spectrum of the LiFePO 4 material obtained in Examples 1, 2, and 3 before carbon coating heat treatment.
图2是实施例1、2、3碳包覆热处理后所得的LiFePO4/C材料的XRD图谱。 Fig. 2 is the XRD spectrum of the LiFePO 4 /C material obtained after carbon-coating heat treatment in Examples 1, 2, and 3.
图3是实施例1碳包覆热处理前所得的LiFePO4材料的SEM图。 Fig. 3 is the SEM image of the LiFePO 4 material obtained before the carbon coating heat treatment in Example 1.
图4是实施例1碳包覆热处理后所得的LiFePO4/C材料的SEM图。 FIG. 4 is an SEM image of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 1. FIG.
图5是实施例2碳包覆热处理前所得的LiFePO4材料的SEM图。 Fig. 5 is the SEM image of the LiFePO 4 material obtained before the carbon coating heat treatment in Example 2.
图6是实施例2碳包覆热处理后所得的LiFePO4/C材料的SEM图。 FIG. 6 is an SEM image of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 2. FIG.
图7是实施例3碳包覆热处理前所得的LiFePO4材料的SEM图。 Fig. 7 is the SEM image of the LiFePO 4 material obtained before the carbon coating heat treatment in Example 3.
图8是实施例3碳包覆热处理后所得的LiFePO4/C材料的SEM图。 Fig. 8 is an SEM image of the LiFePO 4 /C material obtained after the carbon coating heat treatment in Example 3.
图9是实施例1碳包覆热处理后所得的LiFePO4/C材料的TEM图。 FIG. 9 is a TEM image of the LiFePO 4 /C material obtained after carbon-coating heat treatment in Example 1. FIG.
图10是实施例2碳包覆热处理后所得的LiFePO4/C材料的TEM图。 Fig. 10 is a TEM image of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 2.
图11是实施例1碳包覆热处理后所得的LiFePO4/C材料的循环伏安曲线。 Fig. 11 is the cyclic voltammetry curve of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 1.
图12是实施例2碳包覆热处理后所得的LiFePO4/C材料的循环伏安曲线。 Fig. 12 is the cyclic voltammetry curve of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 2.
图13是实施例3碳包覆热处理后所得的LiFePO4/C材料的循环伏安曲线。 Fig. 13 is the cyclic voltammetry curve of the LiFePO 4 /C material obtained after carbon coating heat treatment in Example 3.
具体实施方式 detailed description
下面通过实施例并结合附图对本发明进一步阐述，但并不限制本发明。 The present invention will be further elaborated below by means of embodiments in conjunction with the accompanying drawings, but the present invention is not limited.
实施例1Example 1
取40.5mmol的LiOH.H2O溶解在40ml乙二醇中进行磁力搅拌，待溶解后边搅拌边慢慢滴入22.5mmol的浓磷酸溶液，可以看到有白色悬浮物出现。取15mmol的FeSO4.7H2O一定量的抗坏血酸（FeSO4.7H2O的5%wt）完全溶解在40ml乙二醇中，然后边搅拌边加入到上述的白色悬浮液中，继续搅拌30分钟。FeSO4.7H2O:H3PO4:LiOH·H2O:乙二醇作为反应物且摩尔比为1:1.5:2.7:1.43。将悬浮液移到有聚四氟乙烯内衬的密闭反应釜中，高压反应釜的填装度为75%，将反应釜放到恒温鼓风干燥箱中加热到180℃保温10h后冷却到室温。然后将得到的灰绿色沉淀物用去离子水和酒精反复清洗干净。将洗干净的粉末放入真空干燥箱中干燥数小时，烘干温度控制为70℃。为了实现碳包覆，将磷酸铁锂粉末与聚丙烯一定质量比混合然后在管式真空炉里加热到650℃保温3h，最后获得了所需要的LiFePO4/C。 Dissolve 40.5mmol of LiOH.H 2 O in 40ml of ethylene glycol and perform magnetic stirring. Slowly add 22.5mmol of concentrated phosphoric acid solution while stirring after dissolution, and white suspended matter can be seen. Take 15mmol of FeSO 4 .7H 2 O and a certain amount of ascorbic acid (5%wt of FeSO 4 .7H 2 O) is completely dissolved in 40ml of ethylene glycol, then add it into the above white suspension while stirring, and continue stirring for 30 minute. FeSO 4 .7H 2 O:H 3 PO 4 :LiOH·H 2 O:Ethylene glycol was used as reactant and the molar ratio was 1:1.5:2.7:1.43. Move the suspension to a closed reaction kettle lined with polytetrafluoroethylene. The filling degree of the high-pressure reaction kettle is 75%. Put the reaction kettle in a constant temperature blast drying oven and heat it to 180 ° C for 10 hours, then cool it to room temperature . Then the gray-green precipitate obtained was washed repeatedly with deionized water and alcohol. Put the washed powder into a vacuum drying oven to dry for several hours, and the drying temperature is controlled at 70°C. In order to achieve carbon coating, lithium iron phosphate powder was mixed with polypropylene in a certain mass ratio, and then heated to 650°C for 3 hours in a tube vacuum furnace, and finally the required LiFePO 4 /C was obtained.
实施例2Example 2
取40.5mmol的LiOH.H2O溶解在65ml乙二醇中进行磁力搅拌，待溶解后边搅拌边慢慢滴入22.5mmol的浓磷酸溶液，可以看到有白色悬浮物出现。取15mmol的FeSO4.7H2O一定量的抗坏血酸（FeSO4.7H2O的5%wt）完全溶解在65ml乙二醇中，然后边搅拌边加入到上述的白色悬浮液中，继续搅拌45分钟。FeSO4.7H2O:H3PO4:LiOH·H2O:乙二醇作为反应物且摩尔比为1:1.5:2.7:2.32。将悬浮液移到有聚四氟乙烯内衬的密闭反应釜中，高压反应釜的填装度为75%，将反应釜放到恒温鼓风干燥箱中加热到180℃保温10h后冷却到室温。然后将得到的灰绿色沉淀物用去离子水和酒精反复清洗干净。将洗干净的粉末放入真空干燥箱中干燥数小时，烘干温度控制为75℃。为了实现碳包覆，将磷酸铁锂粉末与聚丙烯一定质量比混合然后在管式真空炉里加热到650℃保温3h，最后获得了所需要的LiFePO4/C。 Take 40.5mmol of LiOH.H 2 O and dissolve it in 65ml of ethylene glycol and stir it magnetically. After dissolving, slowly add 22.5mmol of concentrated phosphoric acid solution while stirring, and a white suspension can be seen. Take 15mmol of FeSO 4 .7H 2 O and a certain amount of ascorbic acid (5%wt of FeSO 4 .7H 2 O) is completely dissolved in 65ml of ethylene glycol, then add it into the above white suspension while stirring, and continue stirring for 45 minute. FeSO 4 .7H 2 O:H 3 PO 4 :LiOH·H 2 O:Ethylene glycol was used as reactant and the molar ratio was 1:1.5:2.7:2.32. Move the suspension to a closed reaction kettle lined with polytetrafluoroethylene. The filling degree of the high-pressure reaction kettle is 75%. Put the reaction kettle in a constant temperature blast drying oven and heat it to 180 ° C for 10 hours, then cool it to room temperature . Then the gray-green precipitate obtained was washed repeatedly with deionized water and alcohol. Put the washed powder into a vacuum drying oven to dry for several hours, and the drying temperature is controlled at 75°C. In order to achieve carbon coating, lithium iron phosphate powder was mixed with polypropylene in a certain mass ratio, and then heated to 650°C for 3 hours in a tube vacuum furnace, and finally the required LiFePO 4 /C was obtained.
实施例3Example 3
取40.5mmol的LiOH.H2O溶解在80ml乙二醇中进行磁力搅拌，待溶解后边搅拌边慢慢滴入22.5mmol的浓磷酸溶液，可以看到有白色悬浮物出现。取15mmol的FeSO4.7H2O一定量的抗坏血酸（FeSO4.7H2O的5%wt）完全溶解在80ml乙二醇中，然后边搅拌边加入到上述的白色悬浮液中，继续搅拌60分钟。FeSO4.7H2O:H3PO4:LiOH·H2O:乙二醇作为反应物且摩尔比为1:1.5:2.7:2.86。将悬浮液移到有聚四氟乙烯内衬的密闭反应釜中，高压反应釜的填装度为75%，将反应釜放到恒温鼓风干燥箱中加热到180℃保温10h后冷却到室温。然后将得到的灰绿色沉淀物用去离子水和酒精反复清洗干净。将洗干净的粉末放入真空干燥箱中干燥数小时，烘干温度控制为80℃。为了实现碳包覆，将磷酸铁锂粉末与聚丙烯一定质量比混合然后在管式真空炉里加热到650℃保温3h，最后获得了所需要的LiFePO4/C。 Dissolve 40.5mmol of LiOH.H 2 O in 80ml of ethylene glycol and stir it magnetically. Slowly add 22.5mmol of concentrated phosphoric acid solution while stirring after dissolving, and white suspended matter can be seen. Take 15mmol of FeSO 4 .7H 2 O and a certain amount of ascorbic acid (5%wt of FeSO 4 .7H 2 O) is completely dissolved in 80ml of ethylene glycol, then add it to the above white suspension while stirring, and continue stirring for 60 minute. FeSO 4 .7H 2 O:H 3 PO 4 :LiOH·H 2 O:Ethylene glycol was used as reactant and the molar ratio was 1:1.5:2.7:2.86. Move the suspension to a closed reaction kettle lined with polytetrafluoroethylene. The filling degree of the high-pressure reaction kettle is 75%. Put the reaction kettle in a constant temperature blast drying oven and heat it to 180 ° C for 10 hours, then cool it to room temperature . Then the gray-green precipitate obtained was washed repeatedly with deionized water and alcohol. Put the cleaned powder into a vacuum drying oven to dry for several hours, and the drying temperature is controlled at 80°C. In order to achieve carbon coating, lithium iron phosphate powder was mixed with polypropylene in a certain mass ratio, and then heated to 650°C for 3 hours in a tube vacuum furnace, and finally the required LiFePO 4 /C was obtained.
实施例4Example 4
将实施例1~3所制备的LiFePO4/C材料分别进行X-射线衍射(BrukerD8advance,德国)实验。实验条件如下：铜靶(λ=0.1518nm)，2q角范围为10~70o。实施例1、2、3碳包覆热处理前所得的LiFePO4材料和碳包覆热处理后所得的LiFePO4/C材料的XRD图谱分别如图1和图2所示。 The LiFePO 4 /C materials prepared in Examples 1-3 were respectively subjected to X-ray diffraction (BrukerD8advance, Germany) experiments. The experimental conditions are as follows: copper target (λ=0.1518nm), 2q angle range is 10~70o. The XRD patterns of the LiFePO 4 material obtained before the carbon coating heat treatment in Examples 1, 2, and 3 and the LiFePO 4 /C material obtained after the carbon coating heat treatment are shown in Figure 1 and Figure 2 , respectively.
从图1和图2中的XRD图谱中可以看到，三种产物的衍射特征峰的强度不同，峰位存在着一致性。所有的衍射峰都能索引到正交晶系的空间结构(JCPDScardNo.81-1173)，这表明合成的磷酸铁锂具有较好的晶体结构。没有观察到杂质衍射峰，这表明合成的样品具有高的相纯度。晶体的择优取向可以通过(020)和(200)这两个晶面的衍射峰强度比值来判断。Kanumara等人认为晶体I(020)/I(200)的值比标准值大的话，则颗粒具有沿着ac晶面择优生长的片状结构。实施例1，2，3热处理前的I(020)/I(200)值分别为4.70，3.35，4.04，热处理之后的值分别为2.86，2.96，3.14，标准值为2.1。这表明晶体颗粒为沿着ac晶面生长的b轴向结构。 It can be seen from the XRD patterns in Figure 1 and Figure 2 that the intensity of the characteristic peaks of the three products is different, and the peak positions are consistent. All the diffraction peaks can be indexed to the spatial structure of the orthorhombic system (JCPDScard No. 81-1173), which indicates that the synthesized lithium iron phosphate has a better crystal structure. No impurity diffraction peaks were observed, which indicated that the synthesized samples had high phase purity. The preferred orientation of the crystal can be judged by the ratio of the diffraction peak intensities of the two crystal planes (020) and (200). Kanumara et al. think that if the value of crystal I(020)/I(200) is larger than the standard value, the particles have a sheet-like structure that preferentially grows along the ac crystal plane. The I(020)/I(200) values of Examples 1, 2, and 3 before heat treatment were 4.70, 3.35, and 4.04, and the values after heat treatment were 2.86, 2.96, and 3.14, respectively, and the standard value was 2.1. This indicates that the crystal grains have a b-axis structure growing along the ac crystal plane.
实施例5Example 5
将实施例1~3所制备的电极材料分别进行SEM(Quanta200FEG)和TEM(FEITecnaiG2F20)实验。实验数据如图3~10所示。 The electrode materials prepared in Examples 1-3 were subjected to SEM (Quanta200FEG) and TEM (FEITecnaiG2F20) experiments respectively. The experimental data are shown in Figures 3-10.
图3，5，7分别为实施例1，2，3碳包覆热处理前所得的LiFePO4材料的SEM图。热处理前，实施例1~3的颗粒分散性好，大小均一，表明样品具有高的结晶度和相纯度。除此之外颗粒都具有片状的结构，实施例1~3的片状颗粒厚度大约为30nm左右。图4，6，8分别为实施例1，2，3碳包覆热处理后所得的LiFePO4/C材料的SEM图。从图中我们可以看出，经过碳包覆热处理后，片状颗粒变厚，颗粒要比热处理前更趋于圆一些。 Figures 3, 5, and 7 are SEM images of the LiFePO 4 material obtained before the carbon coating heat treatment in Examples 1, 2, and 3, respectively. Before heat treatment, the particles of Examples 1-3 had good dispersion and uniform size, indicating that the samples had high crystallinity and phase purity. In addition, the particles all have a flaky structure, and the thickness of the flaky particles in Examples 1 to 3 is about 30 nm. Figures 4, 6, and 8 are SEM images of LiFePO 4 /C materials obtained after carbon-coated heat treatment in Examples 1, 2, and 3, respectively. We can see from the figure that after carbon coating heat treatment, the flake particles become thicker, and the particles tend to be more round than before heat treatment.
图9，10分别实施例1，2碳包覆热处理后所得的LiFePO4/C材料的TEM图。从图中我们可以看出，实施例1，2均为（010）晶面的片状颗粒，即b轴短的片状颗粒。 9 and 10 are TEM images of the LiFePO 4 /C material obtained after carbon-coating heat treatment in Examples 1 and 2, respectively. We can see from the figure that Examples 1 and 2 are both flaky particles with (010) crystal plane, that is, flaky particles with short b-axis.
实施例6Example 6
按质量比电极材料：乙炔黑：粘结剂（聚偏二氟乙烯(PVDF)）＝80：10：10，将实施例1~3所制备的LiFePO4/C电极材料、乙炔黑和粘结剂混合均匀并溶于N-甲基吡咯烷酮(NMP)中，涂在处理过的铂电极上，烘干，即得磷酸铁锂电极正极。将上述所得磷酸铁锂电极正极，铂电极为对电极，1MLi2SO4水溶液为电解液，在电化学工作站进行循环伏安测试。电压区间为-1.8~2.1Vvs.SCE。测试环境为25℃恒温。实验数据如图11~13所示。 According to the mass ratio electrode material: acetylene black: binder (polyvinylidene fluoride (PVDF)) = 80:10:10, the LiFePO 4 /C electrode material prepared in Examples 1~3, acetylene black and binder The agent is mixed uniformly and dissolved in N-methylpyrrolidone (NMP), coated on the treated platinum electrode, and dried to obtain the positive electrode of lithium iron phosphate electrode. Using the positive electrode of the lithium iron phosphate electrode obtained above, the platinum electrode as the counter electrode, and the 1M Li 2 SO 4 aqueous solution as the electrolyte solution, a cyclic voltammetry test was performed on an electrochemical workstation. The voltage range is -1.8~2.1V vs. SCE. The test environment is a constant temperature of 25°C. The experimental data are shown in Figures 11-13.
为了测试样品的电化学性能，对实施例1~3所制备的LiFePO4/C电极材料进行了循环伏安测试。循环伏安测试探究了扫描速率大小对样品在硫酸锂水溶液中发生的氧化还原行为的影响。样品在不同速率下的CV曲线如图11~13所示。图中的一对氧化还原峰对应着锂离子从样品中的嵌入和脱出行为。 In order to test the electrochemical performance of the samples, cyclic voltammetry tests were carried out on the LiFePO 4 /C electrode materials prepared in Examples 1-3. The cyclic voltammetry test explored the influence of the scan rate on the redox behavior of the sample in lithium sulfate aqueous solution. The CV curves of the samples at different rates are shown in Figures 11-13. A pair of redox peaks in the figure correspond to the intercalation and deintercalation behavior of lithium ions from the sample.
从实施例1的CV曲线可以看出，当扫描速率是5~20mV/s时，我们能看到一对明显的氧化还原峰，随着扫描速率变大，峰电流值变大，氧化峰和还原峰分别向正负方向偏移，其间距△E增大，这是因为锂离子在磷酸铁锂中的扩散速度较小，当扫描速率较快时，电极表面的锂离子来不及扩散，促使极化增大而造成的。但扫描速率从50mV/s增大到120mV/s时，这种规律性消失了，出峰越来越不明显，峰电压值反而下降。 As can be seen from the CV curve of Example 1, when the scan rate is 5-20mV/s, we can see a pair of obvious redox peaks. As the scan rate increases, the peak current value becomes larger, and the oxidation peak and The reduction peaks shift to the positive and negative directions respectively, and the distance △E increases. This is because the diffusion rate of lithium ions in lithium iron phosphate is relatively small. caused by the increase. But when the scan rate increases from 50mV/s to 120mV/s, this regularity disappears, the peak is less and less obvious, and the peak voltage value decreases instead.
从实施例2的CV曲线可以看出，当扫描速率是5~20mV/s时，我们能看到一对明显的氧化还原峰，随着扫描速率变大，峰电流值变大，氧化峰和还原峰分别向正负方向偏移，其间距△E增大，这是因为锂离子在磷酸铁锂中的扩散速度较小，当扫描速率较快时，电极表面的锂离子来不及扩散，促使极化增大而造成的。扫描速率从50mV/s开始增大直到280mV/s，曲线仍能出现明显的氧化还原峰，且峰值电压和电流呈现规律性的增加，这表明样品在大扫数下即快速充放电条件下仍能进行锂离子的脱/嵌电化学行为。 As can be seen from the CV curve of Example 2, when the scan rate is 5-20mV/s, we can see a pair of obvious redox peaks. As the scan rate increases, the peak current value becomes larger, and the oxidation peak and The reduction peaks shift to the positive and negative directions respectively, and the distance △E increases. This is because the diffusion rate of lithium ions in lithium iron phosphate is relatively small. caused by the increase. When the scan rate increases from 50mV/s to 280mV/s, the curve can still show obvious redox peaks, and the peak voltage and current increase regularly, which shows that the sample is still stable under the condition of large scan number, that is, fast charge and discharge. Capable of de/intercalating electrochemical behavior of lithium ions.
从实施例3的CV曲线可以看出，当扫描速率是5~50mV/s时，我们能看到一对明显的氧化还原峰，随着扫描速率变大，峰电流值变大，氧化峰和还原峰分别向正负方向偏移，其间距△E增大，这是因为锂离子在磷酸铁锂中的扩散速度较小，当扫描速率较快时，电极表面的锂离子来不及扩散，促使极化增大而造成的。 As can be seen from the CV curve of Example 3, when the scan rate is 5-50mV/s, we can see a pair of obvious redox peaks. As the scan rate increases, the peak current value becomes larger, and the oxidation peak and The reduction peaks shift to the positive and negative directions respectively, and the distance △E increases. This is because the diffusion rate of lithium ions in lithium iron phosphate is relatively small. caused by the increase.
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| CN113707853A (en) * | 2021-07-26 | 2021-11-26 | 清华大学 | Positive electrode composite material, preparation method thereof, positive electrode and lithium battery |
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| CN115732680A (en) * | 2021-08-26 | 2023-03-03 | 北京当升材料科技股份有限公司 | Electrode material with olivine structure and its preparation method and application |
| WO2024198684A1 (en) * | 2023-03-24 | 2024-10-03 | 宁德时代新能源科技股份有限公司 | Composite positive electrode active material, battery cell, battery and electric device |
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