WO2023179046A1 - Preparation method for lithium iron phosphate/carbon composite material and use thereof - Google Patents

Preparation method for lithium iron phosphate/carbon composite material and use thereof Download PDF

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WO2023179046A1
WO2023179046A1 PCT/CN2022/131585 CN2022131585W WO2023179046A1 WO 2023179046 A1 WO2023179046 A1 WO 2023179046A1 CN 2022131585 W CN2022131585 W CN 2022131585W WO 2023179046 A1 WO2023179046 A1 WO 2023179046A1
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carbon
iron phosphate
lithium
source
lithium iron
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PCT/CN2022/131585
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French (fr)
Chinese (zh)
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李玲
李长东
阮丁山
陈若葵
时振栓
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宜昌邦普循环科技有限公司
宜昌邦普宜化新材料有限公司
广东邦普循环科技有限公司
湖南邦普循环科技有限公司
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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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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

Definitions

  • the invention belongs to the technical field of battery materials, and specifically relates to a preparation method and application of lithium iron phosphate/carbon composite materials.
  • the preparation method of lithium iron phosphate is to use iron phosphate as the precursor, lithium carbonate as the lithium source, glucose or other organic carbon as the carbon source, and obtain it through processes such as grinding, spray drying, and sintering.
  • the commonly used synthesis method of ferric phosphate on the market is the precipitation method, that is, ferrous sulfate, a by-product of the titanium dioxide process, is used as the iron source, ammonium dihydrogen phosphate or phosphoric acid is used as the phosphorus source, hydrogen peroxide is used as the oxidant, and ammonia or sodium hydroxide regulates the pH of the reaction process and is precipitated.
  • the dosage of hydrogen peroxide is generally 1.2-1.5 times the theoretical value. The dosage of hydrogen peroxide greatly increases the cost of iron phosphate synthesis.
  • lithium iron phosphate Due to the structural characteristics of lithium iron phosphate, it has defects such as low lithium ion diffusion coefficient and low conductivity. To address this defect, surface carbon coating can effectively improve the ion and electronic conductivity on the surface of lithium iron phosphate particles and between particles; however, there are still problems of low lithium ion diffusion coefficient and conductivity between internal lithium iron phosphate particles, internal particles and the surface layer. , especially in order to increase the compaction density, there will be some large particles.
  • the present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a lithium iron phosphate/carbon composite material and its preparation method and application.
  • the lithium iron phosphate/carbon composite material has electrochemical properties such as excellent conductivity.
  • a lithium iron phosphate/carbon composite material includes carbon-doped lithium iron phosphate and a carbon layer coating the surface of the carbon-doped lithium iron phosphate.
  • the first discharge specific capacity of the lithium iron phosphate/carbon composite material is 156-162 mAh/g.
  • the first charge and discharge efficiency of the lithium iron phosphate/carbon composite material is 97-99%.
  • a preparation method of lithium iron phosphate/carbon composite material including the following steps:
  • the iron source in the iron source solution is elemental iron, ferrous chloride, ferrous sulfate, ferric nitrate, ferrous acetate, ferrous phosphate, pyrite, waste ferric phosphate, At least one type of phosphorus iron slag.
  • the iron element is one of iron powder and iron sheet.
  • the phosphorus source is at least one of phosphoric acid, phosphorous acid, sodium hypophosphite, ammonium hydrogen phosphate, ammonium dihydrogen phosphate or ammonium phosphate.
  • the phosphorus source is at least one of phosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate or ammonium phosphate.
  • step (1) after the iron source solution and the phosphorus source are mixed, the molar ratio of iron and phosphorus is (0.92-1.03):1.
  • the molar ratio of iron and phosphorus is (0.97-1):1.
  • the temperature is raised to a temperature of 40-50°C.
  • carbon-containing iron phosphate dihydrate can be gradually and slowly generated using carbon as the crystal nucleation point.
  • the carbon source is at least one of graphite, carbon nanotubes, graphene, carbon powder or acetylene black.
  • the carbon source is at least one of graphite, carbon nanotubes or carbon powder.
  • the reaction temperature is 70-100°C; further preferably, the reaction temperature is 80-95°C.
  • the reaction time is 1-2 h.
  • the oxidizing agent is at least one of hydrogen peroxide, oxygen, sodium peroxide or ammonium persulfate.
  • the oxidizing agent is at least one of hydrogen peroxide and oxygen.
  • the temperature at which the reaction is continued is 70-100°C.
  • the time for continuing the reaction is 2-10 h, and further preferably, the time for continuing the reaction is 4-8 h.
  • the pulping is performed by pulping the carbon-containing iron phosphate filter cake and water at a solid-liquid ratio of 1g:(5-10) mL to obtain a carbon-containing iron phosphate slurry.
  • the washing is to wash the filtrate after solid-liquid separation until the conductivity of the filtrate is ⁇ 500 ⁇ s/cm.
  • the washing is to wash the filtrate after solid-liquid separation until the conductivity of the filtrate is ⁇ 200 ⁇ s/cm.
  • the drying temperature is 60-120°C, and further preferably, the drying temperature is 90-110°C.
  • the carbon-doped iron phosphate dihydrate has a specific surface area of 12-20 m 2 /g and a Dv50 of 3.5-4.2 cm.
  • the lithium source is at least one of lithium carbonate, lithium hydroxide or lithium dihydrogen phosphate.
  • the carbon source is at least one of glucose, sucrose, starch, carbon black or graphene.
  • the carbon source is sucrose.
  • the calcination temperature is 650-800°C, and further preferably, the calcination temperature is 650-700°C.
  • the calcination time is 6-16h, and further preferably, the calcination time is 6-10h.
  • the calcining atmosphere is an inert atmosphere, and further preferably, the calcining atmosphere is a nitrogen atmosphere.
  • step (3) sand grinding and spray drying are also included before the calcination.
  • the present invention also provides a battery, including the above-mentioned lithium iron phosphate/carbon composite material.
  • carbon is distributed inside the iron phosphate particles or between particles. Further synthesis of carbon-coated and carbon-doped lithium iron phosphate materials is more conducive to the production of lithium iron phosphate particles. Conductive carbon bridges are formed between interior parts, between the interior and surface layers of particles, and between particles, providing transmission channels for lithium ions and electrons, thus improving the electrochemical properties such as the conductivity of lithium iron phosphate.
  • the temperature is raised and the carbon source is added, and then the temperature is continued to be raised.
  • Some of the ferrous iron ions in the iron source solution will participate in the reaction.
  • the oxidant is added and the reaction continues.
  • a carbon-doped orthorhombic iron dihydrate precursor is generated. This process greatly reduces the amount of oxidant.
  • the carbon-doped orthorhombic iron dihydrate dihydrate is then calcined with a carbon source and a lithium source to prepare phosphoric acid.
  • the precursor is carbon-doped orthorhombic iron phosphate dihydrate, it is conducive to lithium embedding during the sintering process, improving the lithium ion diffusion coefficient between the internal particles and the surface layer, eliminating the need for dehydration, and lower costs. Moreover, a lithium iron phosphate/carbon composite material with excellent electrochemical properties was prepared.
  • Figure 1 is an SEM image of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention
  • Figure 2 is a schematic diagram of the carbon distribution in the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention
  • Figure 3 is an XRD pattern of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention.
  • Figure 4 is an SEM image of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention.
  • Figure 5 is an XRD pattern of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention.
  • Figure 6 is an SEM image of the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention.
  • Figure 7 is an XRD pattern of the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention.
  • the preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
  • the preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
  • the preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
  • the preparation method of the lithium iron phosphate/carbon composite material of this comparative example includes the following specific steps:
  • Table 1 shows the physical and chemical results of the ferric phosphate dihydrate products prepared in Examples 1, 2, 3 and Comparative Example 1. It can be seen from Table 1 that
  • the C contents of the ferric phosphate dihydrate products prepared in Examples 1-3 were 1.024%, 4.981% and 5.149% respectively.
  • Figure 1 is an SEM image of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention; it can be seen from the figure that the iron phosphate in Example 1 is composed of prismatic and polygonal particles.
  • Figure 2 is a schematic diagram of carbon distribution in lithium iron phosphate prepared in Example 1 of the present invention.
  • Figure 2 shows the distribution of carbon in lithium iron phosphate, and carbon is distributed inside iron phosphate particles or between particles.
  • Figure 3 is an XRD pattern of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention; it can be seen from the figure that the product obtained in Example 1 is orthorhombic iron phosphate dihydrate, which is different from the single iron phosphate dihydrate obtained by general processes. Oblique crystal system iron phosphate dihydrate; the bottom chart is the standard card chart of iron phosphate dihydrate.
  • Figure 4 is an SEM image of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention; it can be seen from the picture that the ferric phosphate dihydrate in Comparative Example 1 is formed by agglomeration of primary particles of flakes.
  • Figure 5 is an XRD pattern of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention. It can be seen from the figure that the product obtained in Comparative Example 1 is monoclinic ferric phosphate dihydrate; the bottom chart is the standard card chart of ferric phosphate dihydrate.
  • Figure 6 is an SEM of lithium iron phosphate/carbon prepared in Example 1 of the present invention. It can be seen from the figure that the lithium iron phosphate in Example 1 is composed of spherical particles with rounded surfaces.
  • Figure 7 is an XRD pattern of lithium iron phosphate/carbon prepared in Example 1 of the present invention. It can be seen from the figure that the lithium iron phosphate obtained in Example 1 is pure phase and orthorhombic crystal form.
  • Table 1 shows the physical and chemical results of the ferric phosphate dihydrate products prepared in Examples 1, 2, 3 and Comparative Example 1. It can be seen from Table 1 that
  • FIG. 1 is an SEM image of iron phosphate in Example 1. It can be seen from the figure that the iron phosphate in Example 1 is composed of prismatic and polygonal particles.
  • Figure 3 is an XRD pattern of ferric phosphate dihydrate in Example 1. It can be seen from the figure that the product obtained in Example 1 is orthorhombic ferric phosphate dihydrate, which is different from the monoclinic ferric phosphate dihydrate obtained by general processes. .
  • Figure 4 is an SEM image of the ferric phosphate dihydrate of Comparative Example 1.
  • Example 1 Example 2
  • Example 3 Comparative example 1 Fe/% 29.3 29.05 29.16 29.13 P/% 16.6 16.29 16.44 16.51 Fe/P 0.978 0.988 0.983 0.978 C/% 1.257 4.981 5.149 0 Dv50 3.99 3.57 4.05 2.79 BET 13 17.5 15 45.8
  • Table 2 is a comparison of the hydrogen peroxide dosage in Example 1 and Comparative Example 1. It can be seen from the table that under the same iron concentration metal liquid and the same volume, the hydrogen peroxide dosage in Comparative Example 1 is almost three times that of Example 1. Embodiment 1 greatly reduces the amount of hydrogen peroxide, reduces the cost, and obtains orthorhombic iron phosphate dihydrate, which is beneficial to the insertion of lithium.
  • Figure 1 is a schematic diagram of the carbon distribution of lithium iron phosphate particles of the present invention. There are carbon bridges inside the particles, and there is a carbon coating layer on the surface of the particles. This carbon distribution can separate the internal grains of the particles from the grains, the grains from the surface of the particles, and the particles from each other. Interconnection provides a transmission channel for lithium ions and electrons, thereby improving the electrochemical performance of lithium iron phosphate.
  • Table 3 shows the electrochemical properties of lithium iron phosphate batteries prepared in Examples 1, 2, 3 and Comparative Example 1. The specific data are obtained through testing with electrochemical workstations and other equipment. As can be seen from Table 2, the electrochemical performance of the lithium iron phosphate product prepared in Examples 1-3 is obviously better than that of Comparative Example 1, especially Example 1.
  • Example 1 Example 2
  • Example 3 Comparative example 1 First discharge specific capacity (mAh/g) 159.2 157.8 156.4 153.4 First charge and discharge efficiency (%) 98.7 97.6 97.2 95.6 0.5C discharge specific capacity (mAh/g) 153 151.7 150.9 140 1C discharge specific capacity (mAh/g) 147.7 145.2 144.8 132.1 2C discharge specific capacity (mAh/g) 139.4 136 135.1 116.4 5C discharge specific capacity (mAh/g) 129.6 123 121 98.5 10C discharge specific capacity (mAh/g) 118.9 111.7 108.3 80.5

Abstract

The present invention belongs to the technical field of battery materials. Disclosed in the present invention are a lithium iron phosphate/carbon composite material, a preparation method therefor and the use thereof. The lithium iron phosphate/carbon composite material comprises carbon-doped lithium iron phosphate and a carbon layer covering the surface of the carbon-doped lithium iron phosphate. In a carbon-containing iron phosphate precursor synthesized in the present invention, carbon is distributed in the interior of iron phosphate particles or between the particles, and a lithium iron phosphate material is then further synthesized, which is beneficial to forming conductive carbon bridges in the interior of the lithium iron phosphate particles, between the interior of a particle and a surface layer and between the particles, thereby providing a transport channel for lithium ions and electrons, such that the electrochemical performance such as the conductivity of lithium iron phosphate is improved.

Description

磷酸铁锂/碳复合材料的制备方法及其应用Preparation method and application of lithium iron phosphate/carbon composite materials 技术领域Technical field
本发明属于电池材料技术领域，具体涉及磷酸铁锂/碳复合材料的制备方法及其应用。The invention belongs to the technical field of battery materials, and specifically relates to a preparation method and application of lithium iron phosphate/carbon composite materials.
背景技术Background technique
磷酸铁锂的制备方法是以磷酸铁为前驱体，碳酸锂为锂源，葡萄糖或其他有机碳作为碳源，经过研磨、喷雾干燥、烧结等工序而得。市场上磷酸铁常用合成方法是沉淀法，即钛白粉工艺副产品硫酸亚铁作为铁源、磷酸二氢铵或磷酸作为磷源，双氧水作为氧化剂，氨水或氢氧化钠调控反应过程pH沉淀得到。双氧水用量一般为理论值的1.2-1.5倍，双氧水用量大大提高了磷酸铁合成的成本。The preparation method of lithium iron phosphate is to use iron phosphate as the precursor, lithium carbonate as the lithium source, glucose or other organic carbon as the carbon source, and obtain it through processes such as grinding, spray drying, and sintering. The commonly used synthesis method of ferric phosphate on the market is the precipitation method, that is, ferrous sulfate, a by-product of the titanium dioxide process, is used as the iron source, ammonium dihydrogen phosphate or phosphoric acid is used as the phosphorus source, hydrogen peroxide is used as the oxidant, and ammonia or sodium hydroxide regulates the pH of the reaction process and is precipitated. The dosage of hydrogen peroxide is generally 1.2-1.5 times the theoretical value. The dosage of hydrogen peroxide greatly increases the cost of iron phosphate synthesis.
由于磷酸铁锂自身的结构特点，导致其存在锂离子扩散系数和电导率低等缺陷。针对此缺陷，表面碳包覆可以有效的改善磷酸铁锂颗粒表面和颗粒间的离子和电子电导率；但内部磷酸铁锂颗粒间，内部颗粒与表层仍存在锂离子扩散系数和电导率低问题，特别是为了提高压实密度，会有部分大颗粒。Due to the structural characteristics of lithium iron phosphate, it has defects such as low lithium ion diffusion coefficient and low conductivity. To address this defect, surface carbon coating can effectively improve the ion and electronic conductivity on the surface of lithium iron phosphate particles and between particles; however, there are still problems of low lithium ion diffusion coefficient and conductivity between internal lithium iron phosphate particles, internal particles and the surface layer. , especially in order to increase the compaction density, there will be some large particles.
为解决上述问题，亟需研发一种可以改善内部磷酸铁锂颗粒间，内部颗粒与表层仍存在锂离子扩散系数和电导率低问题的磷酸铁锂的制备方法和应用。In order to solve the above problems, it is urgent to develop a preparation method and application of lithium iron phosphate that can improve the problems of low lithium ion diffusion coefficient and conductivity between the internal lithium iron phosphate particles and the internal particles and the surface layer.
发明内容Contents of the invention
本发明旨在至少解决上述现有技术中存在的技术问题之一。为此，本发明提出一种磷酸铁锂/碳复合材料及其制备方法和应用，该磷酸铁锂/碳复合材料具有优异电导率等电化学性能。The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a lithium iron phosphate/carbon composite material and its preparation method and application. The lithium iron phosphate/carbon composite material has electrochemical properties such as excellent conductivity.
为实现上述目的，本发明采用以下技术方案：In order to achieve the above objects, the present invention adopts the following technical solutions:
一种磷酸铁锂/碳复合材料，包括碳掺杂的磷酸铁锂，以及包覆在碳掺杂的磷酸铁锂表面的碳层。A lithium iron phosphate/carbon composite material includes carbon-doped lithium iron phosphate and a carbon layer coating the surface of the carbon-doped lithium iron phosphate.
优选地，所述磷酸铁锂/碳复合材料的首次放电比容量为156-162mAh/g。Preferably, the first discharge specific capacity of the lithium iron phosphate/carbon composite material is 156-162 mAh/g.
优选地，所述磷酸铁锂/碳复合材料的首次充放电效率为97-99％。Preferably, the first charge and discharge efficiency of the lithium iron phosphate/carbon composite material is 97-99%.
一种磷酸铁锂/碳复合材料的制备方法，包括以下步骤：A preparation method of lithium iron phosphate/carbon composite material, including the following steps:
(1)将铁源溶液和磷源混合，升温，加入碳源，继续升温，反应，再加入氧化剂， 继续反应，固液分离，取固相，得到含碳磷酸铁滤饼；(1) Mix the iron source solution and the phosphorus source, raise the temperature, add the carbon source, continue to heat up and react, then add the oxidant, continue the reaction, separate the solid and liquid, take the solid phase, and obtain a carbon-containing iron phosphate filter cake;
(2)将所述含碳磷酸铁滤饼进行制浆，固液分离，洗涤，烘干，得到碳掺杂的二水磷酸铁；(2) The carbon-containing iron phosphate filter cake is pulped, solid-liquid separated, washed, and dried to obtain carbon-doped iron phosphate dihydrate;
(3)将所述碳掺杂的二水磷酸铁、锂源和碳源混合，煅烧，得到所述磷酸铁锂/碳复合材料。(3) Mix the carbon-doped iron phosphate dihydrate, a lithium source and a carbon source, and calcine to obtain the lithium iron phosphate/carbon composite material.
优选地，步骤(1)中，所述铁源溶液中的铁源为铁单质、氯化亚铁、硫酸亚铁、硝酸铁、醋酸亚铁、磷酸亚铁、硫铁矿、废磷酸铁、磷铁渣中的至少一种。Preferably, in step (1), the iron source in the iron source solution is elemental iron, ferrous chloride, ferrous sulfate, ferric nitrate, ferrous acetate, ferrous phosphate, pyrite, waste ferric phosphate, At least one type of phosphorus iron slag.
进一步优选地，所述铁单质为铁粉、铁皮中的一种。Further preferably, the iron element is one of iron powder and iron sheet.
优选地，步骤(1)中，所述磷源为磷酸、亚磷酸、次磷酸钠、磷酸氢铵、磷酸二氢铵或磷酸铵中的至少一种。Preferably, in step (1), the phosphorus source is at least one of phosphoric acid, phosphorous acid, sodium hypophosphite, ammonium hydrogen phosphate, ammonium dihydrogen phosphate or ammonium phosphate.
进一步优选地，所述磷源为磷酸、磷酸氢铵、磷酸二氢铵或磷酸铵中的至少一种。Further preferably, the phosphorus source is at least one of phosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate or ammonium phosphate.
优选地，步骤(1)中，所述铁源溶液和磷源混合后，铁和磷的摩尔比为(0.92-1.03)：1。Preferably, in step (1), after the iron source solution and the phosphorus source are mixed, the molar ratio of iron and phosphorus is (0.92-1.03):1.
进一步优选地，所述铁源溶液和磷源混合后，铁和磷的摩尔比为(0.97-1)：1。Further preferably, after the iron source solution and the phosphorus source are mixed, the molar ratio of iron and phosphorus is (0.97-1):1.
优选地，步骤(1)中，所述升温为升温至温度为40-50℃。Preferably, in step (1), the temperature is raised to a temperature of 40-50°C.
在40-50℃温度下，可以以碳为晶核点，逐渐缓慢生成含碳的二水磷酸铁。At a temperature of 40-50°C, carbon-containing iron phosphate dihydrate can be gradually and slowly generated using carbon as the crystal nucleation point.
优选地，步骤(1)中，所述碳源为石墨、碳纳米管、石墨烯、碳粉或乙炔黑中的至少一种。Preferably, in step (1), the carbon source is at least one of graphite, carbon nanotubes, graphene, carbon powder or acetylene black.
进一步优选地，所述碳源为石墨、碳纳米管或碳粉中的至少一种。Further preferably, the carbon source is at least one of graphite, carbon nanotubes or carbon powder.
优选地，步骤(1)中，所述反应的温度为70-100℃；进一步优选地，所述反应的温度为80-95℃。Preferably, in step (1), the reaction temperature is 70-100°C; further preferably, the reaction temperature is 80-95°C.
优选地，步骤(1)中，所述反应的时间为1-2h。Preferably, in step (1), the reaction time is 1-2 h.
优选地，步骤(1)中，所述氧化剂为双氧水、氧气、过氧化钠或过硫酸铵中的至少一种。Preferably, in step (1), the oxidizing agent is at least one of hydrogen peroxide, oxygen, sodium peroxide or ammonium persulfate.
进一步优选地，所述氧化剂为双氧水、氧气中的至少一种。Further preferably, the oxidizing agent is at least one of hydrogen peroxide and oxygen.
优选地，步骤(1)中，所述继续反应的温度为70-100℃。Preferably, in step (1), the temperature at which the reaction is continued is 70-100°C.
优选地，步骤(1)中，所述继续反应的时间为2-10h，进一步优选地，所述继续反应的时间为4-8h。Preferably, in step (1), the time for continuing the reaction is 2-10 h, and further preferably, the time for continuing the reaction is 4-8 h.
优选地，步骤(2)中，所述制浆是将含碳磷酸铁滤饼和水按固液比为1g:(5-10)mL，进行制浆，得到含碳磷酸铁浆液。Preferably, in step (2), the pulping is performed by pulping the carbon-containing iron phosphate filter cake and water at a solid-liquid ratio of 1g:(5-10) mL to obtain a carbon-containing iron phosphate slurry.
优选地，步骤(2)中，所述洗涤是将固液分离后的滤液洗涤至滤液的电导率≤500μs/cm。Preferably, in step (2), the washing is to wash the filtrate after solid-liquid separation until the conductivity of the filtrate is ≤500 μs/cm.
进一步优选地，所述洗涤是将固液分离后的滤液洗涤至滤液的电导率≤200μs/cm。Further preferably, the washing is to wash the filtrate after solid-liquid separation until the conductivity of the filtrate is ≤200 μs/cm.
优选地，步骤(2)中，所述烘干的温度为60-120℃，进一步优选地，所述烘干的温度为90-110℃。Preferably, in step (2), the drying temperature is 60-120°C, and further preferably, the drying temperature is 90-110°C.
优选地，步骤(2)中，所述碳掺杂的二水磷酸铁的比表面积为12-20m 2/g、Dv50为3.5-4.2cm。 Preferably, in step (2), the carbon-doped iron phosphate dihydrate has a specific surface area of 12-20 m 2 /g and a Dv50 of 3.5-4.2 cm.
优选地，步骤(3)中，所述锂源为碳酸锂、氢氧化锂或磷酸二氢锂中的至少一种。Preferably, in step (3), the lithium source is at least one of lithium carbonate, lithium hydroxide or lithium dihydrogen phosphate.
优选地，步骤(3)中，所述碳源为葡萄糖、蔗糖、淀粉、碳黑或石墨烯中的至少一种。Preferably, in step (3), the carbon source is at least one of glucose, sucrose, starch, carbon black or graphene.
进一步优选地，所述碳源为蔗糖。Further preferably, the carbon source is sucrose.
优选地，步骤(3)中，所述煅烧的温度为650-800℃，进一步优选地，所述煅烧的温度为650-700℃。Preferably, in step (3), the calcination temperature is 650-800°C, and further preferably, the calcination temperature is 650-700°C.
优选地，步骤(3)中，所述煅烧的时间为6-16h，进一步优选地，所述煅烧的时间为6-10h。Preferably, in step (3), the calcination time is 6-16h, and further preferably, the calcination time is 6-10h.
优选地，步骤(3)中，所述煅烧的气氛为惰性气氛，进一步优选地，所述煅烧的气氛为氮气气氛。Preferably, in step (3), the calcining atmosphere is an inert atmosphere, and further preferably, the calcining atmosphere is a nitrogen atmosphere.
优选地，步骤(3)中，所述煅烧前还包括进行砂磨和喷雾干燥。Preferably, in step (3), sand grinding and spray drying are also included before the calcination.
本发明还提供一种电池，包括上述的磷酸铁锂/碳复合材料。The present invention also provides a battery, including the above-mentioned lithium iron phosphate/carbon composite material.
相对于现有技术，本发明的有益效果如下：Compared with the prior art, the beneficial effects of the present invention are as follows:
1、本发明合成的含碳磷酸铁前驱体，碳分布在磷酸铁颗粒内部或者颗粒与颗粒之间，再进一步合成碳包覆和碳掺杂的磷酸铁锂材料，更有利于磷酸铁锂颗粒内部间、颗粒内部与表层、颗粒与颗粒间形成导电碳桥，为锂离子、电子提供传输通道，从而提高了磷酸铁锂的电导率等电化学性能。1. In the carbon-containing iron phosphate precursor synthesized by the present invention, carbon is distributed inside the iron phosphate particles or between particles. Further synthesis of carbon-coated and carbon-doped lithium iron phosphate materials is more conducive to the production of lithium iron phosphate particles. Conductive carbon bridges are formed between interior parts, between the interior and surface layers of particles, and between particles, providing transmission channels for lithium ions and electrons, thus improving the electrochemical properties such as the conductivity of lithium iron phosphate.
2、本发明将铁源溶液和磷源混合后，升温加入碳源，再继续升温，铁源溶液中的部分二价铁离子会参加反应，反应一段时间后，再加入氧化剂后，继续反应，生成碳掺 杂的正交晶系二水磷酸铁前驱体，该过程极大降低了氧化剂的用量，再利用碳掺杂的正交晶系二水磷酸铁、碳源、锂源煅烧制备得到磷酸铁锂/碳材料，由于前驱体为碳掺杂的正交晶系二水磷酸铁，有利于烧结过程锂嵌入，提高了内部颗粒与表层的锂离子扩散系数，不用进行脱水，成本更低，而且制备得到优异电化学性能的磷酸铁锂/碳复合材料。2. In the present invention, after mixing the iron source solution and the phosphorus source, the temperature is raised and the carbon source is added, and then the temperature is continued to be raised. Some of the ferrous iron ions in the iron source solution will participate in the reaction. After a period of reaction, the oxidant is added and the reaction continues. A carbon-doped orthorhombic iron dihydrate precursor is generated. This process greatly reduces the amount of oxidant. The carbon-doped orthorhombic iron dihydrate dihydrate is then calcined with a carbon source and a lithium source to prepare phosphoric acid. For lithium iron/carbon materials, since the precursor is carbon-doped orthorhombic iron phosphate dihydrate, it is conducive to lithium embedding during the sintering process, improving the lithium ion diffusion coefficient between the internal particles and the surface layer, eliminating the need for dehydration, and lower costs. Moreover, a lithium iron phosphate/carbon composite material with excellent electrochemical properties was prepared.
附图说明Description of the drawings
图1为本发明实施例1制备得到碳掺杂的二水磷酸铁的SEM图；Figure 1 is an SEM image of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention;
图2为本发明实施例1制备得到磷酸铁锂/碳复合材料中的碳分布示意图；Figure 2 is a schematic diagram of the carbon distribution in the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention;
图3为本发明实施例1制备得到碳掺杂的二水磷酸铁的XRD图；Figure 3 is an XRD pattern of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention;
图4为本发明对比例1制备得到二水磷酸铁的SEM图；Figure 4 is an SEM image of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention;
图5为本发明对比例1制备得到二水磷酸铁的XRD图；Figure 5 is an XRD pattern of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention;
图6为本发明实施例1制备得到磷酸铁锂/碳复合材料的SEM图；Figure 6 is an SEM image of the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention;
图7为本发明实施例1制备得到磷酸铁锂/碳复合材料的XRD图。Figure 7 is an XRD pattern of the lithium iron phosphate/carbon composite material prepared in Example 1 of the present invention.
具体实施方式Detailed ways
以下将结合实施例对本发明的构思及产生的技术效果进行清楚、完整地描述，以充分地理解本发明的目的、特征和效果。显然，所描述的实施例只是本发明的一部分实施例，而不是全部实施例，基于本发明的实施例，本领域的技术人员在不付出创造性劳动的前提下所获得的其他实施例，均属于本发明保护的范围。The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without exerting creative efforts are all protection scope of the present invention.
实施例1Example 1
本实施例的磷酸铁锂/碳复合材料的制备方法，包括以下具体步骤：The preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
(1)配制混合金属液：将硫酸亚铁加入到搅拌槽中配制成铁浓度为35g/L溶液，接着加入磷酸配成磷浓度为20g/L，搅拌均匀，得到70L的含铁、磷的混合金属液；(1) Prepare mixed metal liquid: Add ferrous sulfate into the stirring tank to prepare a solution with an iron concentration of 35g/L, then add phosphoric acid to prepare a phosphorus concentration of 20g/L, stir evenly, and obtain 70L of iron- and phosphorus-containing solution. mixed metal liquid;
(2)将70L配制好的含铁、磷混合金属液倒入反应容器中，搅拌开启调为450rpm，升温到并加入82g碳纳米管，加热升温到90℃，90℃保温2h后，开始滴加双氧水，双氧水用量为1.25kg，反应结束后，用抽滤瓶进行固体与滤液分离，得到含碳磷酸铁滤饼；(2) Pour 70L of the prepared mixed metal liquid containing iron and phosphorus into the reaction vessel, turn on the stirring to 450rpm, heat it up and add 82g of carbon nanotubes, heat to 90°C, keep it at 90°C for 2 hours, and then start dripping Add hydrogen peroxide, the amount of hydrogen peroxide is 1.25kg. After the reaction is completed, use a suction filter bottle to separate the solid and filtrate to obtain a carbon-containing iron phosphate filter cake;
(3)将分离所得含碳磷酸铁滤饼放入制浆水杯中，加入去离子水搅拌均匀，过滤，再用去离子水反复清洗至洗涤水电导率＜500μs/cm，停止洗涤，取滤饼铺散放入100℃烘箱内烘干，得到碳掺杂的二水磷酸铁；(3) Put the separated carbon-containing iron phosphate filter cake into a pulping water cup, add deionized water, stir evenly, filter, and then wash repeatedly with deionized water until the conductivity of the washing water is <500 μs/cm, stop washing, and take out the filter The cake is spread and dried in a 100°C oven to obtain carbon-doped ferric phosphate dihydrate;
(4)称量9.42kg碳掺杂的二水磷酸铁、1.88kg碳酸锂和580g蔗糖混合，砂磨、喷雾得到粉末，将其放入箱式炉内、氮气气氛下，煅烧700℃保温6h，得到磷酸铁锂/碳 复合材料。(4) Weigh 9.42kg of carbon-doped ferric phosphate dihydrate, 1.88kg of lithium carbonate and 580g of sucrose, mix them, grind and spray to obtain a powder, put it into a box-type furnace under a nitrogen atmosphere, and calcine at 700°C for 6 hours. , obtaining lithium iron phosphate/carbon composite materials.
实施例2Example 2
本实施例的磷酸铁锂/碳复合材料的制备方法，包括以下具体步骤：The preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
(1)配制混合金属液：将硫酸亚铁加入到搅拌槽中配制成铁浓度为39g/L溶液，接着加入磷酸配成磷浓度为22.3g/L，搅拌均匀，得到含铁、磷的混合金属液；(1) Prepare mixed metal liquid: Add ferrous sulfate into the stirring tank to prepare a solution with an iron concentration of 39g/L, then add phosphoric acid to prepare a phosphorus concentration of 22.3g/L, stir evenly, and obtain a mixture containing iron and phosphorus. liquid metal;
(2)将70L配制好的含铁、磷混合金属液倒入反应容器中，搅拌开启调为450rpm，升温到并加入457g石墨，加热升温到90℃，90℃保温2h后，开始通入氧气，氧化2h，反应结束后，用抽滤瓶进行固体与滤液分离，得到含碳磷酸铁滤饼；(2) Pour 70L of the prepared mixed metal liquid containing iron and phosphorus into the reaction vessel, turn on the stirring and adjust to 450rpm, heat it up and add 457g of graphite, heat to 90°C, keep it at 90°C for 2 hours, and start to introduce oxygen. , oxidize for 2 hours. After the reaction is completed, use a suction filter bottle to separate the solid and filtrate to obtain a carbon-containing iron phosphate filter cake;
(3)将分离所得含碳磷酸铁滤饼放入制浆水杯中，加入去离子水搅拌均匀，过滤，再用去离子水反复清洗至洗涤水电导率＜500μs/cm，停止洗涤，取滤饼铺散放入100℃烘箱内烘干，得到碳掺杂的二水磷酸铁；(3) Put the separated carbon-containing iron phosphate filter cake into a pulping water cup, add deionized water, stir evenly, filter, and then wash repeatedly with deionized water until the conductivity of the washing water is <500 μs/cm, stop washing, and take out the filter The cake is spread and dried in a 100°C oven to obtain carbon-doped ferric phosphate dihydrate;
(4)称量9.42kg碳掺杂的二水磷酸铁、1.88kg碳酸锂和580蔗糖混合，砂磨、喷雾得到粉末，放入箱式炉内、氮气气氛下，煅烧710℃保温6h，得到磷酸铁锂/碳复合材料。(4) Weigh 9.42kg carbon-doped iron phosphate dihydrate, 1.88kg lithium carbonate and 580 sucrose, mix them, sand grind and spray to obtain the powder, put it into a box-type furnace under a nitrogen atmosphere, and calcine at 710°C for 6 hours to obtain Lithium iron phosphate/carbon composite.
实施例3Example 3
本实施例的磷酸铁锂/碳复合材料的制备方法，包括以下具体步骤：The preparation method of the lithium iron phosphate/carbon composite material of this embodiment includes the following specific steps:
(1)配制混合金属液：将硫酸亚铁加入到搅拌槽中配制成铁浓度为38.4g/L溶液，接着加入磷酸配成磷浓度为21.9g/L，搅拌均匀，得到含铁、磷的混合金属液；(1) Prepare mixed metal liquid: Add ferrous sulfate into the stirring tank to prepare a solution with an iron concentration of 38.4g/L, then add phosphoric acid to prepare a phosphorus concentration of 21.9g/L, stir evenly, and obtain a solution containing iron and phosphorus. mixed metal liquid;
(2)将70L配制好的含铁、磷混合金属液倒入反应容器中，搅拌开启调为450rpm，升温到并加入457g石墨，加热升温到90℃，90℃保温2h后，开始滴加双氧水，双氧水用量为1.36kg，反应结束后，用抽滤瓶进行固体与滤液分离，得到含碳磷酸铁滤饼；(2) Pour 70L of the prepared mixed metal liquid containing iron and phosphorus into the reaction vessel, turn on the stirring and adjust to 450rpm, heat it up and add 457g of graphite, heat to 90°C, keep it at 90°C for 2 hours, and then start adding hydrogen peroxide dropwise , the dosage of hydrogen peroxide is 1.36kg. After the reaction, use a suction filter bottle to separate the solid and filtrate to obtain a carbon-containing iron phosphate filter cake;
(3)将分离所得含碳磷酸铁滤饼放入制浆水杯中，加入去离子水搅拌均匀，过滤，再用去离子水反复清洗至洗涤水电导率＜500μs/cm，停止洗涤，取滤饼铺散放入100℃烘箱内烘干，得到碳掺杂的二水磷酸铁；(3) Put the separated carbon-containing iron phosphate filter cake into a pulping water cup, add deionized water, stir evenly, filter, and then wash repeatedly with deionized water until the conductivity of the washing water is <500 μs/cm, stop washing, and take out the filter The cake is spread and dried in a 100°C oven to obtain carbon-doped ferric phosphate dihydrate;
(4)称量9.42kg碳掺杂的二水磷酸铁、1.88kg碳酸锂和580g蔗糖混合，砂磨、喷雾得到粉末，之后将其放入箱式炉内、氮气气氛下，煅烧710℃保温6h，得到磷酸铁锂/碳复合材料。(4) Weigh 9.42kg of carbon-doped iron phosphate dihydrate, 1.88kg of lithium carbonate and 580g of sucrose, mix them, grind and spray them to obtain a powder, and then put it into a box-type furnace under a nitrogen atmosphere and calcine at 710°C to keep it warm. After 6h, the lithium iron phosphate/carbon composite material was obtained.
对比例1(在生成二水磷酸铁过程前加入氧化剂)Comparative Example 1 (adding oxidizing agent before generating ferric phosphate dihydrate)
本对比例的磷酸铁锂/碳复合材料的制备方法，包括以下具体步骤：The preparation method of the lithium iron phosphate/carbon composite material of this comparative example includes the following specific steps:
(1)配制混合金属液：将硫酸亚铁加入到搅拌槽中配制成铁浓度为35g/L溶液，接着加入磷酸配成磷浓度为20g/L，搅拌均匀，得到含铁、磷的混合金属液；(1) Prepare mixed metal liquid: Add ferrous sulfate into the stirring tank to prepare a solution with an iron concentration of 35g/L, then add phosphoric acid to prepare a phosphorus concentration of 20g/L, stir evenly, and obtain a mixed metal containing iron and phosphorus. liquid;
(2)将70L配制好的含铁、磷混合金属液倒入反应容器中，为了将二价铁充分氧化需要加入3.7kg双氧水，氧化完后，搅拌开启调为450rpm，并加入碱液调整pH为2.0，加热升温到90℃陈化4h，用抽滤瓶进行固体与滤液分离，得到磷酸铁滤饼；(2) Pour 70L of the prepared mixed metal liquid containing iron and phosphorus into the reaction vessel. In order to fully oxidize the ferrous iron, 3.7kg of hydrogen peroxide needs to be added. After oxidation, turn on the stirring to 450rpm, and add alkali solution to adjust the pH. is 2.0, heat to 90°C and age for 4 hours, use a suction filter bottle to separate the solid and filtrate, and obtain the iron phosphate filter cake;
(3)将分离所得磷酸铁滤饼放入制浆水杯中，加入去离子水搅拌均匀，过滤，再用去离子水反复清洗至洗涤水电导率＜500μs/cm，停止洗涤，取滤饼铺散放入100℃烘箱内烘干，得到二水磷酸铁；(3) Put the separated iron phosphate filter cake into a pulping water cup, add deionized water, stir evenly, filter, and then wash repeatedly with deionized water until the conductivity of the washing water is <500 μs/cm, stop washing, and take out the filter cake to spread Pour it into powder and dry it in an oven at 100℃ to obtain ferric phosphate dihydrate;
(4)称量7.54kg二水磷酸铁、1.88kg碳酸锂和蔗糖混合，砂磨、喷雾得到粉末，之后将其放入箱式炉内、氮气气氛下，煅烧700℃保温6h，得到磷酸铁锂/碳复合材料。理化结果：(4) Weigh 7.54kg ferric phosphate dihydrate, 1.88kg lithium carbonate and sucrose, mix, sand grind and spray to obtain powder, then put it into a box furnace under a nitrogen atmosphere, calcine at 700°C for 6 hours to obtain ferric phosphate Lithium/carbon composite. Physical and chemical results:
表1为实施例1、2、3与对比例1制备的二水磷酸铁产品的理化结果。由表1可知，Table 1 shows the physical and chemical results of the ferric phosphate dihydrate products prepared in Examples 1, 2, 3 and Comparative Example 1. It can be seen from Table 1 that
实施例1-3中制备得到二水磷酸铁产品中C含量分别为1.024％、4.981％和5.149％。The C contents of the ferric phosphate dihydrate products prepared in Examples 1-3 were 1.024%, 4.981% and 5.149% respectively.
图1为本发明实施例1制备得到碳掺杂的二水磷酸铁的SEM图；从图可以看出实施例1的磷酸铁是由棱状、多边形颗粒组成。Figure 1 is an SEM image of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention; it can be seen from the figure that the iron phosphate in Example 1 is composed of prismatic and polygonal particles.
图2为本发明实施例1制备得到磷酸铁锂中的碳分布示意图；图2可得碳在磷酸铁锂中的分布，碳分布在磷酸铁颗粒内部或者颗粒与颗粒之间。Figure 2 is a schematic diagram of carbon distribution in lithium iron phosphate prepared in Example 1 of the present invention; Figure 2 shows the distribution of carbon in lithium iron phosphate, and carbon is distributed inside iron phosphate particles or between particles.
图3为本发明实施例1制备得到碳掺杂的二水磷酸铁的XRD图；从图中可以看出实施例1所得产品为正交晶系二水磷酸铁，不同于一般工艺所得的单斜晶系二水磷酸铁；底部图谱为二水磷酸铁标准卡片图谱。Figure 3 is an XRD pattern of carbon-doped iron phosphate dihydrate prepared in Example 1 of the present invention; it can be seen from the figure that the product obtained in Example 1 is orthorhombic iron phosphate dihydrate, which is different from the single iron phosphate dihydrate obtained by general processes. Oblique crystal system iron phosphate dihydrate; the bottom chart is the standard card chart of iron phosphate dihydrate.
图4为本发明对比例1制备得到二水磷酸铁的SEM图；从图中可以看出对比例1的二水磷酸铁是由薄片一次粒子团聚而成。Figure 4 is an SEM image of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention; it can be seen from the picture that the ferric phosphate dihydrate in Comparative Example 1 is formed by agglomeration of primary particles of flakes.
图5为本发明对比例1制备得到二水磷酸铁的XRD图。从图中可以看出对比例1所得的产品为单斜晶系二水磷酸铁；底部图谱为二水磷酸铁标准卡片图谱。Figure 5 is an XRD pattern of ferric phosphate dihydrate prepared in Comparative Example 1 of the present invention. It can be seen from the figure that the product obtained in Comparative Example 1 is monoclinic ferric phosphate dihydrate; the bottom chart is the standard card chart of ferric phosphate dihydrate.
图6为本发明实施例1制备得到磷酸铁锂/碳的SEM。从图中可以看出实施例1的磷酸铁锂是由表面圆润的球状颗粒组成。Figure 6 is an SEM of lithium iron phosphate/carbon prepared in Example 1 of the present invention. It can be seen from the figure that the lithium iron phosphate in Example 1 is composed of spherical particles with rounded surfaces.
图7为本发明实施例1制备得到磷酸铁锂/碳的XRD图。从图中可以看出实施例1所得为纯相、正交晶型的磷酸铁锂。Figure 7 is an XRD pattern of lithium iron phosphate/carbon prepared in Example 1 of the present invention. It can be seen from the figure that the lithium iron phosphate obtained in Example 1 is pure phase and orthorhombic crystal form.
理化结果：Physical and chemical results:
表1为实施例1、2、3与对比例1制备的二水磷酸铁产品的理化结果。由表1可知，Table 1 shows the physical and chemical results of the ferric phosphate dihydrate products prepared in Examples 1, 2, 3 and Comparative Example 1. It can be seen from Table 1 that
实施例1-3中制备得到二水磷酸铁产品中C含量分别为1.024％、4.981％和5.149％。图2为实施例1磷酸铁的SEM图，从图可以看出实施例1的磷酸铁是由棱状、多边形颗粒组成。图3为实施例1的二水磷酸铁的XRD图，从图中可以看出实施例1所得产品为正交晶系二水磷酸铁，不同于一般工艺所得的单斜晶系二水磷酸铁。图4为对比例1的二水磷酸铁的SEM图，从图中可以看出对比例1的二水磷酸铁是由薄片一次粒子团聚而成。图5为对比例1的二水磷酸铁的XRD图，从图中可以看出对比例1所得的产品为单斜晶系二水磷酸铁。The C contents of the ferric phosphate dihydrate products prepared in Examples 1-3 were 1.024%, 4.981% and 5.149% respectively. Figure 2 is an SEM image of iron phosphate in Example 1. It can be seen from the figure that the iron phosphate in Example 1 is composed of prismatic and polygonal particles. Figure 3 is an XRD pattern of ferric phosphate dihydrate in Example 1. It can be seen from the figure that the product obtained in Example 1 is orthorhombic ferric phosphate dihydrate, which is different from the monoclinic ferric phosphate dihydrate obtained by general processes. . Figure 4 is an SEM image of the ferric phosphate dihydrate of Comparative Example 1. It can be seen from the picture that the ferric phosphate dihydrate of Comparative Example 1 is formed by agglomeration of primary particles of flakes. Figure 5 is an XRD pattern of ferric phosphate dihydrate in Comparative Example 1. It can be seen from the figure that the product obtained in Comparative Example 1 is monoclinic ferric phosphate dihydrate.
表1二水磷酸铁产品中的理化结果Table 1 Physical and chemical results in ferric phosphate dihydrate products
 ​ 实施例1Example 1 实施例2Example 2 实施例3Example 3 对比例1Comparative example 1
Fe/％Fe/% 29.329.3 29.0529.05 29.1629.16 29.1329.13
P/％P/% 16.616.6 16.2916.29 16.4416.44 16.5116.51
Fe/PFe/P 0.9780.978 0.9880.988 0.9830.983 0.9780.978
C/％C/% 1.2571.257 4.9814.981 5.1495.149 00
Dv50Dv50 3.993.99 3.573.57 4.054.05 2.792.79
BETBET 1313 17.517.5 1515 45.845.8
表2为实施例1和对比例1的双氧水用量比较，从表中可以看出，相同的铁浓度金属液、相同体积下，对比例1的双氧水用量几乎是实施例1的3倍。实施例1大大降低了双氧水用量，降低成本，并得到了正交晶系的二水磷酸铁，有利于锂的嵌入。Table 2 is a comparison of the hydrogen peroxide dosage in Example 1 and Comparative Example 1. It can be seen from the table that under the same iron concentration metal liquid and the same volume, the hydrogen peroxide dosage in Comparative Example 1 is almost three times that of Example 1. Embodiment 1 greatly reduces the amount of hydrogen peroxide, reduces the cost, and obtains orthorhombic iron phosphate dihydrate, which is beneficial to the insertion of lithium.
表2实施例1和对比例1的双氧水用量比较Table 2 Comparison of hydrogen peroxide dosage between Example 1 and Comparative Example 1
Figure PCTCN2022131585-appb-000001
Figure PCTCN2022131585-appb-000001
电化学性能：Electrochemical properties:
图1为本发明磷酸铁锂颗粒碳分布示意图，颗粒内部存在碳桥架，颗粒表面有碳包覆层，此碳分布可以将颗粒内部晶粒与晶粒间、晶粒与颗粒表面、颗粒与颗粒间连接，提供了锂离子、电子传输通道，从而提高磷酸铁锂电化学性能。Figure 1 is a schematic diagram of the carbon distribution of lithium iron phosphate particles of the present invention. There are carbon bridges inside the particles, and there is a carbon coating layer on the surface of the particles. This carbon distribution can separate the internal grains of the particles from the grains, the grains from the surface of the particles, and the particles from each other. Interconnection provides a transmission channel for lithium ions and electrons, thereby improving the electrochemical performance of lithium iron phosphate.
表3为实施例1、2、3与对比例1制备得到磷酸铁锂电池的电化学性能，具体数据是通过电化学工作站等设备测试得到。由表2可知，实施例1-3中制备得到磷酸铁锂产品的电化学性能明显比对比例1要好，特别是实施例1。Table 3 shows the electrochemical properties of lithium iron phosphate batteries prepared in Examples 1, 2, 3 and Comparative Example 1. The specific data are obtained through testing with electrochemical workstations and other equipment. As can be seen from Table 2, the electrochemical performance of the lithium iron phosphate product prepared in Examples 1-3 is obviously better than that of Comparative Example 1, especially Example 1.
表3磷酸铁锂电池的电化学性能对比Table 3 Comparison of electrochemical performance of lithium iron phosphate batteries
电化学性能Electrochemical properties 实施例1Example 1 实施例2Example 2 实施例3Example 3 对比例1Comparative example 1
首次放电比容量(mAh/g)First discharge specific capacity (mAh/g) 159.2159.2 157.8157.8 156.4156.4 153.4153.4
首次充放电效率(％)First charge and discharge efficiency (%) 98.798.7 97.697.6 97.297.2 95.695.6
0.5C放电比容量(mAh/g)0.5C discharge specific capacity (mAh/g) 153153 151.7151.7 150.9150.9 140140
1C放电比容量(mAh/g)1C discharge specific capacity (mAh/g) 147.7147.7 145.2145.2 144.8144.8 132.1132.1
2C放电比容量(mAh/g)2C discharge specific capacity (mAh/g) 139.4139.4 136136 135.1135.1 116.4116.4
5C放电比容量(mAh/g)5C discharge specific capacity (mAh/g) 129.6129.6 123123 121121 98.598.5
10C放电比容量(mAh/g)10C discharge specific capacity (mAh/g) 118.9118.9 111.7111.7 108.3108.3 80.580.5
本发明不限于上述实施例，在所属技术领域普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下作出各种变化。此外，在不冲突的情况下，本发明的实施例及实施例中的特征可以相互组合。The present invention is not limited to the above-described embodiments. Various changes can be made within the knowledge scope of those of ordinary skill in the art without departing from the gist of the present invention. In addition, the embodiments of the present invention and the features in the embodiments may be combined with each other without conflict.

Claims (10)

  1. 一种磷酸铁锂/碳复合材料，其特征在于，包括碳掺杂的磷酸铁锂，以及包覆在碳掺杂的磷酸铁锂表面的碳层。A lithium iron phosphate/carbon composite material is characterized by including carbon-doped lithium iron phosphate and a carbon layer coating the surface of the carbon-doped lithium iron phosphate.
  2. 根据权利要求1所述的磷酸铁锂/碳复合材料，其特征在于，所述磷酸铁锂/碳复合材料的首次放电比容量为156-162mAh/g。The lithium iron phosphate/carbon composite material according to claim 1, wherein the first discharge specific capacity of the lithium iron phosphate/carbon composite material is 156-162 mAh/g.
  3. 根据权利要求1所述的磷酸铁锂/碳复合材料，其特征在于，所述磷酸铁锂/碳复合材料的首次充放电效率为97-99％。The lithium iron phosphate/carbon composite material according to claim 1, wherein the first charge and discharge efficiency of the lithium iron phosphate/carbon composite material is 97-99%.
  4. 权利要求1-3中任一项所述的磷酸铁锂/碳复合材料的制备方法，其特征在于，包括以下步骤：The preparation method of lithium iron phosphate/carbon composite material according to any one of claims 1-3, characterized in that it includes the following steps:
    (1)将铁源溶液和磷源混合，升温，加入碳源，继续升温，反应，再加入氧化剂，继续反应，固液分离，取固相，得到含碳磷酸铁滤饼；(1) Mix the iron source solution and the phosphorus source, raise the temperature, add the carbon source, continue to heat up and react, then add the oxidant, continue the reaction, separate the solid and liquid, take the solid phase, and obtain a carbon-containing iron phosphate filter cake;
    (2)将所述含碳磷酸铁滤饼进行制浆，固液分离，洗涤，烘干，得到碳掺杂的二水磷酸铁；(2) The carbon-containing iron phosphate filter cake is pulped, solid-liquid separated, washed, and dried to obtain carbon-doped iron phosphate dihydrate;
    (3)将所述碳掺杂的二水磷酸铁、锂源和碳源混合，煅烧，得到所述磷酸铁锂/碳复合材料。(3) Mix the carbon-doped iron phosphate dihydrate, a lithium source and a carbon source, and calcine to obtain the lithium iron phosphate/carbon composite material.
  5. 根据权利要求4所述的制备方法，其特征在于，步骤(1)中，所述铁源溶液中的铁源为铁单质、氯化亚铁、硫酸亚铁、硝酸铁、醋酸亚铁、磷酸亚铁、硫铁矿、废磷酸铁、磷铁渣中的至少一种；所述磷源为磷酸、亚磷酸、次磷酸钠、磷酸氢铵、磷酸二氢铵或磷酸铵中的至少一种。The preparation method according to claim 4, characterized in that, in step (1), the iron source in the iron source solution is elemental iron, ferrous chloride, ferrous sulfate, ferric nitrate, ferrous acetate, phosphoric acid At least one of ferrous iron, pyrite, waste iron phosphate, and iron phosphate slag; the phosphorus source is at least one of phosphoric acid, phosphorous acid, sodium hypophosphite, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, or ammonium phosphate. .
  6. 根据权利要求4所述的制备方法，其特征在于，步骤(1)中，所述铁源溶液和磷源混合后，铁和磷的摩尔比为(0.92-1.03)：1；所述继续反应的温度为70-100℃，所述继续反应的时间为2-10h。The preparation method according to claim 4, characterized in that, in step (1), after the iron source solution and the phosphorus source are mixed, the molar ratio of iron and phosphorus is (0.92-1.03): 1; the continued reaction The temperature is 70-100°C, and the time for continuing the reaction is 2-10h.
  7. 根据权利要求4所述的制备方法，其特征在于，步骤(1)中，所述碳源为石墨、碳纳米管、石墨烯、碳粉或乙炔黑中的至少一种；所述氧化剂为双氧水、氧气、过氧化钠或过硫酸铵中的至少一种。The preparation method according to claim 4, characterized in that, in step (1), the carbon source is at least one of graphite, carbon nanotubes, graphene, carbon powder or acetylene black; the oxidant is hydrogen peroxide , at least one of oxygen, sodium peroxide or ammonium persulfate.
  8. 根据权利要求4所述的制备方法，其特征在于，步骤(3)中，所述锂源为碳酸锂、氢氧化锂或磷酸二氢锂中的至少一种。The preparation method according to claim 4, characterized in that in step (3), the lithium source is at least one of lithium carbonate, lithium hydroxide or lithium dihydrogen phosphate.
  9. 根据权利要求4所述的制备方法，其特征在于，步骤(3)中，所述碳源为葡萄 糖、蔗糖、淀粉、碳黑或石墨烯中的至少一种。The preparation method according to claim 4, characterized in that in step (3), the carbon source is at least one of glucose, sucrose, starch, carbon black or graphene.
  10. 一种电池，其特征在于，包括权利要求1-3中任一项所述的磷酸铁锂/碳复合材料。A battery, characterized by comprising the lithium iron phosphate/carbon composite material according to any one of claims 1-3.
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