Brief Introduction of Preparation Method of Lithium Ion Cathode Material Lithium Iron Phosphate

Lithium iron phosphate exists in the form of a lithium iron phosphate ore in nature and has an ordered olivine structure. The chemical formula of lithium iron phosphate is: LiMPO4, wherein lithium is positive monovalent; central metal iron is positive divalent; phosphate is negative trivalent, and is often used as a cathode material for lithium batteries. Lithium iron phosphate batteries are used in energy storage equipment, power tools, light electric vehicles, large electric vehicles, small equipment and mobile power. Among them, lithium iron phosphate for new energy electric vehicles accounts for about 45% of total lithium iron phosphate.

Second, lithium iron phosphate as lithium battery cathode material

Compared with other lithium battery cathode materials, the olivine-structured lithium iron phosphate has the advantages of safety, environmental protection, low cost, long cycle life and high temperature performance, and is one of the most promising cathode materials for lithium ion batteries.

High security performance

The lithium iron phosphate crystal has a stable PO bond, which is difficult to decompose. When overcharged and high temperature, there is no structural collapse or heat generation or strong oxide formation, and the overcharge safety is high.

Long cycle life

The lead-acid battery has a cycle life of about 300 times and a service life of between 1 and 1.5 years. The number of cycles of lithium iron phosphate battery can reach 2000 or above, and the theoretical service life can reach 7-8 years.

Good temperature performance

The peak temperature of lithium iron phosphate can reach 350 ° C -500 ° C, while lithium manganate and lithium cobalt oxide are only about 200 ° C.

Environmental protection

Lithium iron phosphate batteries are generally considered to be free of heavy metals and rare metals, non-toxic, non-polluting, and are absolutely green batteries.

The mechanism of charge and discharge of lithium iron phosphate as a positive electrode material is different from other traditional materials. The charge and discharge involved in the electrochemical reaction is the iron phosphate two phase of lithium iron phosphate. The charge and discharge reaction is as follows:

Charging reaction:

Discharge reaction:

When charging, Li+ is separated from LiFePO4, and Fe2+ loses one electron to become Fe3+; when discharged, Li+ is inserted into iron phosphate to become LiFePO4. The change of Li+ occurs at the interface of LiFePO4/FePO4, so the charge-discharge curve is very flat and the potential is stable, which is suitable for electrode materials.

Third, the preparation of lithium iron phosphate

The raw material for preparing lithium iron phosphate is abundant. Some common lithium sources, iron sources, carbon sources, and phosphorus sources are as follows:

The preparation of lithium iron phosphate powder affects its performance as a positive electrode material to some extent. At present, there are many methods for preparing lithium iron phosphate, such as a high temperature solid phase reaction method, a carbothermal reduction method, and a hydrothermal method, a spray pyrolysis method, a sol-gel method, a coprecipitation method, and the like which have not been scaled up.

High temperature solid phase reaction

The high temperature solid phase reaction method is the most mature and widely used method for preparing lithium iron phosphate. The iron source, the lithium source and the phosphorus source are uniformly mixed and dried in a stoichiometric ratio, and then sintered in an inert atmosphere for 5 to 10 hours at a lower temperature (300 to 350 ° C) to initially decompose the raw materials and then at a high temperature (The olivine-type lithium iron phosphate is obtained by sintering at 600~800 ° C for 10-20 hours.

The high-temperature solid-phase synthesis of lithium iron phosphate is simple in process and easy to control. The disadvantages are that the crystal size is large, the particle size is difficult to control, the distribution is uneven, the morphology is irregular, and the product magnification characteristics are poor.

2. Carbothermal reduction method

The carbothermal reduction method is to add a carbon source (starch, sucrose, etc.) as a reducing agent in the raw material mixing, and is usually used together with a high-temperature solid phase method. The carbon source can reduce Fe3+ to Fe2+ in high-temperature calcination, thereby avoiding Fe2+ during the reaction. Turning into Fe3+ makes the synthesis process more reasonable, but the reaction time is relatively long and the control of the conditions is more stringent.

3. Spray pyrolysis

Spray pyrolysis is an effective means of obtaining a lithium iron phosphate powder having a uniform particle size and a regular shape. The precursor is sprayed into the reactor at 450 to 650 ° C with the carrier gas, and lithium iron phosphate is obtained after the high temperature reaction. The precursor prepared by spray pyrolysis has a high sphericity and a uniform particle size distribution. After high temperature reaction, a spherical lithium iron phosphate is obtained. The spheroidization of lithium iron phosphate is beneficial to increase the specific surface area of the material and increase the volume specific energy of the material.

4. Hydrothermal method

The hydrothermal method belongs to the liquid phase synthesis method, which means that the water is used as a solvent in a sealed pressure vessel, and the chemical reaction is carried out under high temperature and high pressure conditions by a raw material, and the nano precursor is obtained after being washed and dried by filtration, and finally calcined at a high temperature. After that, lithium iron phosphate can be obtained. Hydrothermal preparation of lithium iron phosphate has the advantages of easy control of crystal form and particle size, uniform phase, small particle size and simple process, but requires high temperature and high pressure equipment, high cost and complicated process.

In addition to the above methods, there are various methods such as a coprecipitation method, a sol-gel method, an oxidation-reduction method, an emulsification drying method, and a microwave sintering method.

Fourth, summary

Although lithium iron phosphate is prepared in many ways, most of them are in the laboratory research stage except for the industrial application of high temperature solid phase reaction. With the deepening of research on the preparation and modification of lithium iron phosphate, the industrialization speed of lithium iron phosphate as a positive electrode material will continue to accelerate. To learn more about the latest industrialization of lithium iron phosphate cathode material lithium iron phosphate, please sign up for the 2017 Energy Granular Materials Preparation and Testing Technology Symposium held on October 16-17. At that time, Professor Guorong Hu from Central South University will share with you the report on the progress of industrialization of lithium iron phosphate cathode material lithium iron phosphate.

Director of Institute of Light Metal and Industrial Electrochemistry, School of Metallurgy and Environment, Central South University, Deputy Director of Engineering Research Center of Advanced Battery Materials, Ministry of Education, Director of China Chemical and Physical Power Association, Director of china lithium battery Association, Editor of International Power Supply, Lithium Battery Communication Editorial board.

He is mainly engaged in the research of electrochemical theory and application, energy materials, etc., and has made outstanding achievements in the research and development and industrialization of lithium ion battery cathode materials. He has presided over and participated in more than 20 national, provincial and ministerial research projects, including one of the major industrialization projects of the National Development and Reform Commission, one of the “863” projects of the Ministry of Science and Technology, and one of the national science and technology support plan projects, and the National Torch Program And a number of key science and technology projects in Hunan Province. The company has achieved outstanding results in the industrialization of lithium ion battery cathode materials, and successfully realized the industrialization of lithium cobaltate, lithium manganate and lithium iron phosphate.

Workshop on 2017 Energy Granular Materials Preparation and Testing Technology

The conference aims to provide a communication platform for domestic and foreign scholars and industry professionals to research energy particle materials applications, strengthen industry information exchange, and contribute to the breakthrough of lithium battery, capacitor, fuel cell and electric vehicle battery technology.

Organizer: China Particle Society Energy Granular Materials Committee, China Powder Network

Co-organizer: Nuremberg Exhibition (Shanghai) Co., Ltd.

Sponsor: Hosokawa Mikron (Shanghai) Powder Machinery Co., Ltd., Dandong Baite Instrument Co., Ltd., Jiangsu Miyou Powder New Equipment Manufacturing Co., Ltd.

Supporting units: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Institute of Process Engineering, Chinese Academy of Sciences, Tsinghua University, Institute of Physics, Chinese Academy of Sciences, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China Battery Industry Association, China Super Capacitor Industry Alliance, Dongguan Yifu Machinery Technology Co., Ltd., Shijiazhuang Rijia Powder Equipment Technology Co., Ltd., Jiangsu Gaozhun Intelligent Equipment Co., Ltd., Linyi County Chasing Electromechanical Equipment Co., Ltd., Guangzhou Zhongzhuo Intelligent Equipment Co., Ltd., Shenzhen Boyi Chemical Machinery Co., Ltd. , Malvern Instrument Co., Ltd., Xinxiang Haomai Machinery Equipment Co., Ltd., Jiangsu Qianjin Furnace Equipment Co., Ltd.

Meeting highlights

Highlight 1: Policy interpretation of energy pellets;

Highlight 2: From the perspective of particle preparation, examine the advantages and disadvantages of core energy materials such as lithium batteries, sodium batteries, super-capacitors, and fuel cells;

Highlight 3: Explore new energy particles (such as graphene, carbon nanotubes, ternary lithium battery anodes, sodium ion battery electrodes, metal lithium) technology and its application in the energy storage and conversion industry;

Highlight 4: Exchange of the latest technological achievements in the field of energy pellet materials and industry leaders;

Highlight 5: Exhibition and conference, lithium battery materials, super-capacitor manufacturing equipment, testing technology and application one-stop display.

Highlight 6: Project docking. A number of domestic lithium batteries, lithium battery materials manufacturers, new project leaders in the field of raw materials, equipment, equipment procurement consulting.

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