Method for preparing positive electrode material lithium iron phosphate of lithium ion battery

Abstract

The invention discloses a method for preparing a positive electrode material lithium iron phosphate of a lithium ion battery. The method comprises the following steps: uniformly mixing a ferric iron source, a lithium source, a phosphate source, a reducing agent, a doping element compound and a conductive agent or a conductive agent precursor in a certain proportion and performing reaction to makethe ferric iron source reduced to a ferrous iron source; and calcinating and crystallizing a mixture containing ferrous iron at a relatively low temperature to obtain the lithium iron phosphate with fine particles and excellent performance. The preparation method of the lithium iron phosphate has low raw material cost and simple and easy process, and the obtained lithium iron phosphate material has high specific capacity and excellent cycling performance and is suitable for industrial production.

Description

technical field [0001] The invention relates to a method for preparing a cathode material of a lithium ion battery, and more specifically relates to a method for preparing lithium iron phosphate, an anode material of a lithium ion battery, by adopting a step-by-step reaction process. Background technique [0002] LiMn 2 o 4 、LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 and LiFePO 4 It is considered to be a positive electrode material for large-scale power lithium-ion batteries, among which lithium iron phosphate is considered to be the most promising positive electrode material due to its rich source of raw materials, low cost, safety and excellent cycle performance. In order to realize the practical application of lithium iron phosphate as soon as possible, a lot of research has been done on the preparation method of lithium iron phosphate as the positive electrode material of lithium ion battery. At present, the preparation methods of lithium iron phosphate mainly include carbothermal...

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Problems solved by technology

[0003] Chinese patent CN1564343A and U.S. patent US6528033B1 disclose the carbothermal reduction method developed from the traditional high-temperature solid-phase method. Using the reducibility of carbon at high temperature, ferric iron is reduced to prepare lithium iron phosphate with smaller particles. Electrochemical The performance has been improved, but the solid-phase reaction is basically a solid-solid interface reaction. The preparation requires long-term ball milling and heat treatment, which leads to a long preparation cycle and increased cost. In addition, long-term heat treatment will cause the grain growth of the material, which is not conducive to Improve the ionic conductivity of the material

[0004] Chinese patent CN1431147A disclosed liquid phase reaction method [also refer to WO02 / 083555A2 and document [J] Chem.Mater.20,4560 (2008) and document [J] Angew.Chem.Int.Ed.47, 1 (2008) 〕Can prepare lithium iron phosphate nanomaterials with uniform particles or core-shell structure, but in order to obtain nanomaterials or ensure the purity of materials, templates or inert environments are required. The process control is relatively strict and the process is complicated, which is not conducive to industrialization

[0005] Chinese patent CN1469499A and literature [J] J.Electrochem.Soc., 149 (7) A886-890 (2002) discloses the synthesis of LiFePO by chemical lithium intercalation method 4 The material method, the method adopts the nano-scale iron phosphate raw material, in the organic solution, the lithium iron phosphate of amorphous nanometer is obtained through LiI reduction and chemical intercalation, and then the crystal form LiFePO with excellent electrochemical performance can be obtained through high temperature treatment. 4 , the LiI raw material used in this process is expensive and not suitable for industrialization

[0006] Hydrothermal method (document [J] Electrochem.Commun.3,505 (2001)) and Chinese patent CN1581537A all can obtain relatively pure LiFePO in the microwave method disclosed on February 16, 2005 4 However, these two methods have very strict requirements on process conditions and require special experimental equipment, such as high-pressure reactors, etc., and it is difficult to meet the requirements of large-scale preparation of lithium iron phosphate battery cathode materials

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