WO2023226550A1 - 高导电性磷酸铁锂的制备方法及其应用 - Google Patents

高导电性磷酸铁锂的制备方法及其应用 Download PDF

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WO2023226550A1
WO2023226550A1 PCT/CN2023/081943 CN2023081943W WO2023226550A1 WO 2023226550 A1 WO2023226550 A1 WO 2023226550A1 CN 2023081943 W CN2023081943 W CN 2023081943W WO 2023226550 A1 WO2023226550 A1 WO 2023226550A1
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preparation
iron phosphate
lithium iron
mixed solution
source
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PCT/CN2023/081943
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English (en)
French (fr)
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余海军
谢英豪
李爱霞
张学梅
李长东
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广东邦普循环科技有限公司
湖南邦普循环科技有限公司
湖南邦普汽车循环有限公司
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Publication of WO2023226550A1 publication Critical patent/WO2023226550A1/zh

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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/626—Metals
    • 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
    • H01M4/36—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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 lithium battery cathode materials, and specifically relates to a preparation method and application of highly conductive lithium iron phosphate.
  • lithium iron phosphate batteries Compared with ternary batteries, lithium iron phosphate batteries have higher safety and lower cost advantages. They have the advantages of good thermal stability, long cycle life, environmental friendliness, and rich sources of raw materials. They are currently the most potential power source. Lithium-ion battery cathode materials are gaining favor from more automobile manufacturers, and their market share continues to increase. In China, represented by BYD, the market share remains high. Especially in the energy storage market, lithium iron phosphate has broad application prospects.
  • the current mainstream direction is to use wet synthesis of iron phosphate, and then sinter the iron phosphate with the lithium source and then coat it with conductive carbon.
  • the iron salt solution and phosphate are added to the stirrer in parallel.
  • Mixing and co-precipitation are carried out in the reactor.
  • a large amount of salt remains in the mother liquor.
  • ammonia water is added as a complexing agent during the co-precipitation process. This not only consumes a large amount of ammonia and other materials, but also produces a large amount of waste gas, waste water and waste, thereby placing a huge burden on the environment.
  • the conductivity of the lithium iron phosphate material prepared by this method is relatively poor, and its intrinsic conductivity is 10 -10 ⁇ 10 -9 s/cm.
  • Traditional carbon black and graphite conductive agents can effectively fill the gaps between positive electrode material particles, but the remote particle connection effect is poor, the conductivity is limited, the local conductivity is uneven, and small particles of conductive carbon black SP are easily trapped in the gaps of the active material. The electrical conductivity becomes worse.
  • Conductivity can be improved to a certain extent by carbon coating lithium iron phosphate, but it is difficult to essentially solve the problem of poor conductivity and will lead to a reduction in specific capacity. How to improve the conductivity of lithium iron phosphate while reducing the impact of contrast capacity has become an urgent technical problem to be solved.
  • 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 preparation method and application of highly conductive lithium iron phosphate.
  • the lithium iron phosphate cathode material prepared by this method has high conductivity and avoids the poor conductivity and specificity caused by carbon coating. Problems such as low capacity.
  • a method for preparing highly conductive lithium iron phosphate which includes the following steps:
  • step S1 the molar ratio of Li, Fe, P, and Bi in the mixed solution is (300-360): (98-102): (98-102): (2-8) .
  • step S1 the concentration of iron element in the mixed solution is 0.3-0.6 mol/L.
  • the reducing agent is at least one of ascorbic acid, alginic acid, yellow dextrin, glucose or soluble starch.
  • step S1 the concentration of the reducing agent in the mixed solution is 5-10 g/L.
  • the ferrous iron source is at least one of ferrous sulfate or ferrous chloride.
  • the phosphorus source is at least one of phosphoric acid, dihydrogen phosphate, monohydrogen phosphate or phosphate.
  • step S2 the temperature of the hydrothermal reaction is 160-220°C. Further, the hydrothermal reaction time is 1-4 h.
  • step S2 the cooling is to rapidly cool the reacted material to room temperature in cooling water at 0-10°C.
  • step S3 the drying process is: vacuum drying at 100-120°C for 6-12 hours.
  • step S3 the calcination temperature is 500-650°C. Further, the calcination time is 3-5h.
  • the invention also provides the application of the preparation method in preparing lithium ion batteries.
  • the present invention synthesizes lithium iron phosphate cathode material through a hydrothermal method.
  • bismuth ammonium citrate and a reducing agent undergo an oxidation-reduction reaction to generate bismuth element (the conductivity of bismuth is two orders of magnitude higher than that of ordinary amorphous carbon.
  • the carbon in conventionally prepared carbon-coated iron phosphate cathode materials is mostly amorphous carbon and has poor conductivity), which disperses the metal bismuth into the synthesized lithium iron phosphate precipitate, thus improving the conductivity of the material and obtaining high conductivity.
  • Lithium iron phosphate cathode material is mostly amorphous carbon and has poor conductivity
  • the present invention uses the hydrothermal reduction of bismuth to form metallic bismuth to improve the conductivity of the material. While further calcining to stabilize the crystal form of the material, the invention utilizes the low melting point characteristics of metallic bismuth to further uniformly disperse the metallic bismuth and make the material have local conductivity differences. reduce. Compared with lithium iron phosphate obtained by conventional technology (solid-phase sintering of iron phosphate, lithium source, and carbon source), this method reduces the amount of carbon coating, giving the material higher specific capacity and conductivity.
  • Figure 1 is an SEM image of the highly conductive lithium iron phosphate prepared in Example 1 of the present invention.
  • a highly conductive lithium iron phosphate is prepared.
  • the specific process is:
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it to 180°C at a heating rate of 5°C/min for hydrothermal reaction for 2 hours;
  • Step 3 Put the hydrothermal reaction kettle directly into the cooling water at 5°C and quickly cool it to room temperature, and separate the solid and liquid to obtain solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with anhydrous ethanol, and then vacuum-dry it at 110°C for 8 hours to obtain a dry material;
  • Step 5 Calculate the dried material at 550°C for 4 hours under nitrogen gas protection to obtain highly conductive lithium iron phosphate.
  • a highly conductive lithium iron phosphate is prepared.
  • the specific process is:
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it up to 160°C at a heating rate of 3°C/min for hydrothermal reaction for 4 hours;
  • Step 3 Put the hydrothermal reaction kettle directly into 0°C cooling water and quickly cool it to room temperature, and separate the solid and liquid to obtain a solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with anhydrous ethanol, and then vacuum-dry it at 100°C for 12 hours to obtain a dry material;
  • Step 5 Calculate the dried material at 500°C for 5 hours under nitrogen gas protection to obtain highly conductive lithium iron phosphate.
  • a highly conductive lithium iron phosphate is prepared.
  • the specific process is:
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it up to 220°C at a heating rate of 8°C/min for hydrothermal reaction for 1 hour;
  • Step 3 Put the hydrothermal reaction kettle directly into 10°C cooling water and quickly cool it to room temperature, and separate the solid and liquid to obtain a solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with absolute ethanol, and then vacuum-dry it at 120°C for 6 hours to obtain a dry material;
  • Step 5 Calculate the dried material at 650°C for 3 hours under nitrogen gas protection to obtain highly conductive lithium iron phosphate.
  • This comparative example prepared a carbon-coated lithium iron phosphate.
  • the main difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not add bismuth ammonium citrate and added carbon source for coating.
  • the specific process is:
  • the concentration of iron in the mixed solution is 0.5 mol/L. ;
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it to 180°C at a heating rate of 5°C/min for hydrothermal reaction for 2 hours;
  • Step 3 Put the hydrothermal reaction kettle directly into the cooling water at 5°C and quickly cool it to room temperature, and separate the solid and liquid to obtain a solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with anhydrous ethanol, and then vacuum-dry it at 110°C for 8 hours to obtain a dry material;
  • Step 5 Add deionized water to the dry material and glucose at a mass ratio of 100:15, mix and stir thoroughly in the mixing tank, spray dry, keep at 580°C for 9 hours in an inert atmosphere, and pulverize to obtain Carbon-coated lithium iron phosphate.
  • This comparative example prepared a carbon-coated lithium iron phosphate.
  • the main difference between Comparative Example 2 and Example 2 is that Comparative Example 2 did not add bismuth ammonium citrate and added carbon source for coating.
  • the specific process is:
  • the concentration of iron element in the mixed solution is 0.3mol/L;
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it up to 160°C at a heating rate of 3°C/min for hydrothermal reaction for 4 hours;
  • Step 3 Put the hydrothermal reaction kettle directly into the cooling water at 0°C and quickly cool it to room temperature, and separate the solid and liquid to obtain solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with anhydrous ethanol, and then vacuum-dry it at 100°C for 12 hours to obtain a dry material;
  • Step 5 Add deionized water to the dry material and glucose at a mass ratio of 100:15, mix and stir thoroughly in the mixing tank, spray dry, keep at 580°C for 9 hours in an inert atmosphere, and pulverize to obtain Carbon-coated lithium iron phosphate.
  • This comparative example prepared a carbon-coated lithium iron phosphate.
  • the main difference between Comparative Example 3 and Example 3 is that Comparative Example 3 did not add bismuth ammonium citrate and added carbon source for coating.
  • the specific process is:
  • the concentration of iron in the mixed solution is 0.6 mol. /L;
  • Step 2 Put the mixed solution into a hydrothermal reactor and seal it, and heat it up to 220°C at a heating rate of 8°C/min for hydrothermal reaction for 1 hour;
  • Step 3 Put the hydrothermal reaction kettle directly into 10°C cooling water and quickly cool it to room temperature, and separate the solid and liquid to obtain a solid material;
  • Step 4 Wash the solid material with deionized water first, then wash it with absolute ethanol, and then vacuum-dry it at 120°C for 6 hours to obtain a dry material;
  • Step 5 Add deionized water to the dry material and glucose at a mass ratio of 100:15, mix and stir thoroughly in the mixing tank, spray dry, keep at 580°C for 9 hours in an inert atmosphere, and pulverize to obtain Carbon-coated lithium iron phosphate.
  • the lithium iron phosphate obtained in the examples and comparative examples, acetylene black as the conductive agent, and PVDF as the binder were mixed at a mass ratio of 8:1:1, and a certain amount of organic solvent NMP was added, stirred and then coated on aluminum foil
  • the positive electrode sheet is made on the above, and the negative electrode is made of metallic lithium sheet;
  • the separator is Celgard2400 polypropylene porous membrane;
  • the solvent in the electrolyte is a solution composed of EC, DMC and EMC in a mass ratio of 1:1:1, and the solute is LiPF 6 , LiPF 6 Concentration is 1.0mol/L; assembled in glove box Model 2023 button cell battery.
  • the resistivity of the prepared positive electrode sheet was tested with a four-probe resistivity tester, and the battery was tested for charge and discharge cycle performance.
  • the discharge specific capacity of 0.1C and 1C was tested in the cut-off voltage range of 2.2 to 4.3V. The results are shown in Table 1. shown.
  • the resistivity and discharge specific capacity of the embodiment are higher than those of the comparative example, indicating that compared with the carbon-coated lithium iron phosphate, the lithium iron phosphate doped with a small amount of metal bismuth has better conductive properties and higher specific capacity.

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Abstract

本发明公开了一种高导电性磷酸铁锂的制备方法及其应用，所述制备方法包括以下步骤：将柠檬酸铋铵、磷源、锂源、亚铁源、还原剂和水混合；将所得混合溶液进行水热反应，固液分离得到固体料；将固体料置于惰性气氛下煅烧，即得高导电性磷酸铁锂。本发明在合成过程中通过柠檬酸铋铵与还原剂发生氧化还原反应生成铋单质，使金属铋分散到合成的磷酸铁锂沉淀物中，从而提升材料的导电性，得到高导电性的磷酸铁锂正极材料。

Description

高导电性磷酸铁锂的制备方法及其应用 技术领域
本发明属于锂电池正极材料技术领域，具体涉及一种高导电性磷酸铁锂的制备方法及其应用。
背景技术
磷酸铁锂电池相对于三元电池具备更高的安全性和更低的成本优势，其具备热稳定性好、循环寿命长、环境友好，原料来源丰富等优势，是目前最具应用潜力的动力锂离子电池正极材料，正获得更多汽车厂商的青睐，市场占有率不断提升。国内以比亚迪为代表，市场占有率居高不下，尤其在储能市场，磷酸铁锂具有广阔的应用前景。
针对磷酸铁锂正极材料的制备，目前主流方向是采用湿法合成磷酸铁，然后将磷酸铁与锂源烧结之后再包覆导电碳，具体地，将铁盐溶液和磷酸盐并流加入到搅拌反应器中进行混合共沉淀，共沉淀结晶后大量盐保留在母液中，同时共沉淀过程中添加氨水作为络合剂，不仅需要消耗大量的氨等物料，而且还会产生大量的废气、废水和废物，从而对环境造成巨大的负担。
此外，该方法制备的磷酸铁锂材料的导电性比较差，其本征电导率为10-10～10-9s/cm。传统的炭黑及石墨类导电剂能有效填充正极材料颗粒间隙，但远程颗粒连接效果较差，导电能力受限，局部电导能力不均匀，并且小颗粒导电炭黑SP易陷于活性材料空隙中，导电性能变差。通过对磷酸铁锂进行碳包覆可以在一定程度上提到导电性，但是难以从本质上解决导电性不佳的问题，且会导致比容量降低。如何提高磷酸铁锂电导率的同时减少对比容量的影响，成为亟待解决的技术难题。
发明内容
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，本发明提出一种高导电性磷酸铁锂的制备方法及其应用，该方法制备得到的磷酸铁锂正极材料具有较高的导电能力，避免了碳包覆带来的导电性差、比容量低等问题。
根据本发明的一个方面，提出了一种高导电性磷酸铁锂的制备方法，包括以下步骤：
S1：将柠檬酸铋铵、磷源、锂源、亚铁源、还原剂和水混合，得到混合溶液；
S2：将所述混合溶液进行水热反应，反应结束后冷却，固液分离，得到固体料；
S3：所述固体料经洗涤、干燥，再置于惰性气氛下煅烧，即得所述高导电性磷酸铁锂。
在本发明的一些实施方式中，步骤S1中，混合溶液中Li、Fe、P、Bi的摩尔比为(300-360)：(98-102)：(98-102)：(2-8)。
在本发明的一些实施方式中，步骤S1中，所述混合溶液中铁元素的浓度为0.3-0.6mol/L。
在本发明的一些实施方式中，步骤S1中，所述还原剂为抗坏血酸、海藻酸、黄糊精、葡萄糖或可溶性淀粉中的至少一种。
在本发明的一些实施方式中，步骤S1中，所述混合溶液中还原剂的浓度为5-10g/L。
在本发明的一些实施方式中，步骤S1中，所述亚铁源为硫酸亚铁或氯化亚铁中的至少一种。
在本发明的一些实施方式中，步骤S1中，所述磷源为磷酸、磷酸二氢盐、磷酸一氢盐或磷酸盐中的至少一种。
在本发明的一些实施方式中，步骤S2中，所述水热反应的温度为160-220℃。进一步地，所述水热反应的时间为1-4h。
在本发明的一些实施方式中，步骤S2中，所述冷却是将反应后物料在0-10℃的冷却水中快速冷却至室温。
在本发明的一些实施方式中，步骤S3中，所述干燥的过程为：在100-120℃下真空干燥6-12h。
在本发明的一些实施方式中，步骤S3中，所述煅烧的温度为500-650℃。进一步地，所述煅烧的时间为3-5h。
本发明还提供所述的制备方法在制备锂离子电池中的应用。
根据本发明的一种优选的实施方式，至少具有以下有益效果：
1、本发明通过水热法合成磷酸铁锂正极材料，在合成过程中通过柠檬酸铋铵与还原剂发生氧化还原反应生成铋单质(铋的导电性比普通的无定形碳高两个数量级，常规制备的碳包覆磷酸铁正极材料中的碳多为无定形碳，导电性较差)，使金属铋分散到合成的磷酸铁锂沉淀物中，从而提升材料的导电性，得到高导电性的磷酸铁锂正极材料。
2、本发明利用铋的水热还原形成金属铋，提高材料导电性，在后续进一步煅烧稳定材料晶型的同时，利用金属铋低熔点特性，使金属铋进一步均匀分散，使材料局部导电性差异降低。该方法与常规技术(磷酸铁、锂源、碳源固相烧结)得到的磷酸铁锂相比，减少了碳包覆的量，使材料具有更高的比容量和电导率。
附图说明
下面结合附图和实施例对本发明做进一步的说明，其中：
图1为本发明实施例1制备的高导电性磷酸铁锂SEM图。
具体实施方式
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。
实施例1
本实施例制备了一种高导电性磷酸铁锂，具体过程为：
步骤1，先将柠檬酸铋铵溶于去离子水中，再加入磷酸、氢氧化锂、硫酸亚铁以及黄糊精，配制成元素摩尔比Li:Fe:P:Bi＝330:100:100:5的混合溶液，混合溶液中铁元素的浓度为0.5mol/L，还原剂的浓度为7g/L；
步骤2，将混合溶液放入水热反应釜密闭，以5℃/min的升温速率升温至180℃水热反应2h；
步骤3，将水热反应釜直接放入5℃的冷却水中快速冷却至室温，固液分离，得到 固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于110℃真空干燥8h，得到干燥料；
步骤5，将干燥料在氮气气体保护下于550℃煅烧4h，得到高导电性磷酸铁锂。
实施例2
本实施例制备了一种高导电性磷酸铁锂，具体过程为：
步骤1，先将柠檬酸铋铵溶于去离子水中，再加入磷酸二氢铵、氢氧化锂、氯化亚铁以及葡萄糖，配制成元素摩尔比Li:Fe:P:Bi＝300:100:100:2的混合溶液，混合溶液中铁元素的浓度为0.3mol/L，还原剂的浓度为5g/L；
步骤2，将混合溶液放入水热反应釜密闭，以3℃/min的升温速率升温至160℃水热反应4h；
步骤3，将水热反应釜直接放入0℃的冷却水中快速冷却至室温，固液分离，得到固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于100℃真空干燥12h，得到干燥料；
步骤5，将干燥料在氮气气体保护下于500℃煅烧5h，得到高导电性磷酸铁锂。
实施例3
本实施例制备了一种高导电性磷酸铁锂，具体过程为：
步骤1，先将柠檬酸铋铵溶于去离子水中，再加入磷酸钠、氯化锂、氯化亚铁以及可溶性淀粉，配制成元素摩尔比Li:Fe:P:Bi＝360:100:100:8的混合溶液，混合溶液中铁元素的浓度为0.6mol/L，还原剂的浓度为10g/L；
步骤2，将混合溶液放入水热反应釜密闭，以8℃/min的升温速率升温至220℃水热反应1h；
步骤3，将水热反应釜直接放入10℃的冷却水中快速冷却至室温，固液分离，得到固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于120℃真空干燥6h，得到干燥料；
步骤5，将干燥料在氮气气体保护下于650℃煅烧3h，得到高导电性磷酸铁锂。
对比例1
本对比例制备了一种碳包覆的磷酸铁锂，对比例1与实施例1的主要区别在于，对比例1未加入柠檬酸铋铵，加入碳源包覆，具体过程为：
步骤1，将磷酸、氢氧化锂、硫酸亚铁溶于去离子水，配制成元素摩尔比Li:Fe:P＝330:100:100的混合溶液，混合溶液中铁元素的浓度为0.5mol/L；
步骤2，将混合溶液放入水热反应釜密闭，以5℃/min的升温速率升温至180℃水热反应2h；
步骤3，将水热反应釜直接放入5℃的冷却水中快速冷却至室温，固液分离，得到固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于110℃真空干燥8h，得到干燥料；
步骤5，将干燥料与葡萄糖按质量比为100:15加入去离子水，在混合搅拌缸里面充分混合、搅拌，再经喷雾干燥后在惰性气氛、580℃下保持9小时，粉碎，即得碳包覆的磷酸铁锂。
对比例2
本对比例制备了一种碳包覆的磷酸铁锂，对比例2与实施例2的主要区别在于，对比例2未加入柠檬酸铋铵，加入碳源包覆，具体过程为：
步骤1，将磷酸二氢铵、氢氧化锂、氯化亚铁溶于去离子水，配制成元素摩尔比Li:Fe:P＝300:100:100的混合溶液，混合溶液中铁元素的浓度为0.3mol/L；
步骤2，将混合溶液放入水热反应釜密闭，以3℃/min的升温速率升温至160℃水热反应4h；
步骤3，将水热反应釜直接放入0℃的冷却水中快速冷却至室温，固液分离，得到 固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于100℃真空干燥12h，得到干燥料；
步骤5，将干燥料与葡萄糖按质量比为100:15加入去离子水，在混合搅拌缸里面充分混合、搅拌，再经喷雾干燥后在惰性气氛、580℃下保持9小时，粉碎，即得碳包覆的磷酸铁锂。
对比例3
本对比例制备了一种碳包覆的磷酸铁锂，对比例3与实施例3的主要区别在于，对比例3未加入柠檬酸铋铵，加入碳源包覆，具体过程为：
步骤1，将磷酸钠、氯化锂、氯化亚铁溶于去离子水，配制成元素摩尔比Li:Fe:P＝360:100:100的混合溶液，混合溶液中铁元素的浓度为0.6mol/L；
步骤2，将混合溶液放入水热反应釜密闭，以8℃/min的升温速率升温至220℃水热反应1h；
步骤3，将水热反应釜直接放入10℃的冷却水中快速冷却至室温，固液分离，得到固体料；
步骤4，将固体料先用去离子水洗涤，再用无水乙醇洗涤后，于120℃真空干燥6h，得到干燥料；
步骤5，将干燥料与葡萄糖按质量比为100:15加入去离子水，在混合搅拌缸里面充分混合、搅拌，再经喷雾干燥后在惰性气氛、580℃下保持9小时，粉碎，即得碳包覆的磷酸铁锂。
试验例
以实施例和对比例得到的磷酸铁锂，乙炔黑为导电剂，PVDF为粘结剂，按质量比8:1:1进行混合，并加入一定量的有机溶剂NMP，搅拌后涂覆于铝箔上制成正极片，负极采用金属锂片；隔膜为Celgard2400聚丙烯多孔膜；电解液中溶剂为EC、DMC和EMC按质量比1:1:1组成的溶液，溶质为LiPF6，LiPF6的浓度为1.0mol/L；在手套箱内组装 2023型扣式电池。
对制得的正极片通过四探针电阻率测试仪测试电阻率，对电池进行充放电循环性能测试，在截止电压2.2～4.3V范围内，测试0.1C、1C放电比容量，结果如表1所示。
表1
由表1可见，实施例的电阻率和放电比容量均高于对比例，表明与碳包覆的磷酸铁锂相比，掺有少量金属铋的磷酸铁锂具有更好的导电性能和更高的比容量。
上面结合附图对本发明实施例作了详细说明，但是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。

Claims (10)

  1. 一种高导电性磷酸铁锂的制备方法，其特征在于，包括以下步骤：
    S1：将柠檬酸铋铵、磷源、锂源、亚铁源、还原剂和水混合，得到混合溶液；
    S2：将所述混合溶液进行水热反应，反应结束后冷却，固液分离，得到固体料；
    S3：所述固体料经洗涤、干燥，再置于惰性气氛下煅烧，即得所述高导电性磷酸铁锂。
  2. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，混合溶液中Li、Fe、P、Bi的摩尔比为(300-360)：(98-102)：(98-102)：(2-8)。
  3. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，所述混合溶液中铁元素的浓度为0.3-0.6mol/L。
  4. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，所述还原剂为抗坏血酸、海藻酸、黄糊精、葡萄糖或可溶性淀粉中的至少一种。
  5. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，所述混合溶液中还原剂的浓度为5-10g/L。
  6. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，所述亚铁源为硫酸亚铁或氯化亚铁中的至少一种。
  7. 根据权利要求1所述的制备方法，其特征在于，步骤S1中，所述磷源为磷酸、磷酸二氢盐、磷酸一氢盐或磷酸盐中的至少一种。
  8. 根据权利要求1所述的制备方法，其特征在于，步骤S2中，所述水热反应的温度为160-220℃。
  9. 根据权利要求1所述的制备方法，其特征在于，步骤S3中，所述煅烧的温度为500-650℃。
  10. 如权利要求1-9中任一项所述的制备方法在制备锂离子电池中的应用。
PCT/CN2023/081943 2022-05-24 2023-03-16 高导电性磷酸铁锂的制备方法及其应用 WO2023226550A1 (zh)

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