A kind of preparation method of porous lithium iron phosphate cathode material

Abstract

The present invention relates to a porous lithium iron phosphate positive electrode material preparation method. The technical scheme comprises: dissolving potassium persulfate in deionized water to prepare a solution I with a concentration of 0.1-20 Kg / m<3>; dissolving sodium lauryl sulfate in deionized water to prepare a solution II with a concentration of 0.01-3 Kg / m<3>; obtaining a solution III according to a volume ratio of methyl methacrylate or styrene to the solution II of 1:20-30; obtaining a template agent according to a volume ratio of the solution I to the solution III of 0.1-0.2:1; dissolving a lithium salt in deionized water to prepare a solution IV with a concentration of 5-50 mol / L; obtaining a solution V according to a mass ratio of the lithium salt to an iron salt to a phosphate of 1:1:1; adding 25-67 wt% of the template agent to the solution V, carrying out liquid nitrogen freezing treatment, and drying; and sintering the dried product under a protective atmosphere to obtain the porous lithium iron phosphate positive electrode material. According to the present invention, the operation is easy, the method is suitable for industrial production, and the product has characteristics of controllable pore structure, good diffusion performance and excellent electrochemical property.

Description

technical field [0001] The invention belongs to the technical field of lithium iron phosphate cathode materials. In particular, it relates to a preparation method of a porous lithium iron phosphate cathode material. Background technique [0002] Lithium-ion batteries are widely used in many civil and military applications such as mobile phones, notebook computers, video cameras and digital cameras due to their advantages of high working voltage, large capacity, small self-discharge, good cycle performance, long service life, light weight and small size. field. In the composition of lithium-ion batteries, the cathode material plays a decisive role in its electrochemical performance, safety performance and even the future development direction. Currently, olivine-structured lithium iron phosphate (LiFePO 4 ) has the advantages of good thermal stability, safety and reliability, environmental protection, high specific capacity, and excellent cycle performance. At the same tim...

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Problems solved by technology

[0003] Although LiFePO 4 Cathode materials have many advantages over other cathode materials, but there are also two main disadvantages: ①The intrinsic conductivity of the material is very low, which is not conducive to reversible reactions, especially high-rate discharges; ②Li + The diffusion rate is slow

The two lead to poor high-rate discharge performance and low reversible specific capacity, which limits its large-scale application

Among them, the shape of the porous lithium iron phosphate cathode material prepared by the sol-gel method is irregular, and there are large pores between the material particles, which are prone to serious agglomeration and bridging phenomena, resulting in the porous lithium iron phosphate cathode material being damaged during the discharge process. The problem of incomplete delithiation occurs. In addition, this process is not easy to achieve large-scale production, and the consistency of the product is relatively poor

The porous lithium iron phosphate cathode material prepared by the colloidal crystal template method, such as the patented technology of "A Method for Preparing Porous Lithium-ion Battery Cathode Material" (CN101383409 A), although the pores of the prepared material are regularly arranged, the process requires Pre-prepared colloidal crystal templates, the process is relatively complicated, and it is difficult to mass-produce

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