Method for preparing high-power lithium iron phosphate composite materials

Abstract

The invention relates to a method for preparing high-power lithium iron phosphate composite materials, which belongs to the technical field of the preparation of lithium battery materials. The invention aims to provide the method for preparing the high-power lithium iron phosphate composite materials which can solve the problem that lithium iron phosphate has low electronic conductivity and difficult ion diffusion in high rate discharge. The invention is technically characterized by making carbon nanotubes reflux in concentrated nitric acid containing iron salt, adding ammonia water and hydroxide ions in a lithium source into the concentrated nitric acid to react to obtain iron hydroxide suspension solution embedded with the carbon nanotubes; then adding phosphate solution into the iron hydroxide suspension solution to obtain iron phosphate suspension solution embedded with the carbon nanotubes; and performing distillation on the iron phosphate suspension solution under reduced pressure to obtain a precursor of the lithium iron phosphate, and grinding the precursor and performing high-temperature sintering in a reductive and inert atmosphere to obtain the high-conductivity lithium iron phosphate composite materials. The lithium iron phosphate composite materials have good shapes with an average grain diameter of 10 to 100nm and excellent electrochemical performance, are particularly suitable for ultrahigh rate discharge requirement, and can meet the requirement of sustained 30C discharge and pulse 100C discharge.

Description

technical field [0001] The invention relates to a preparation method of a high-power lithium iron phosphate composite material, belonging to the technical field of lithium battery material preparation. Background technique [0002] Lithium iron phosphate has become the preferred cathode material for lithium power batteries because of its excellent safety performance and excellent cycle performance. In addition, lithium iron phosphate is also widely used in UPS power supply systems of mobile phones, notebook computers, digital cameras and a large number of other emerging IT products. At present, lithium iron phosphate batteries have begun to substantially replace traditional lead-acid batteries in large-scale power batteries such as electric vehicles, electric tools, automotive 42V batteries, and photovoltaic energy storage batteries. [0003] In the field of electric tools, due to the high requirements on the discharge rate, it is generally required to continue to discharge...

AI Technical Summary

Problems solved by technology

[0003] In the field of electric tools, due to the high requirements on the discharge rate, it is generally required to continue to discharge at 10C, while the particles prepared by the traditional solid-state reaction method are relatively large (the average size of the primary particles is about 0.5um), and the electronic conductivity and ion diffusivity are relatively large. Poor reasons have restricted the application range of lithium iron phosphate batteries

Currently commercially available batteries made of lithium iron phosphate materials have two significant defects at high currents: one is that the voltage is reduced due to the polarization effect of discharge at a higher rate, and the average voltage after discharge at 10C generally does not exceed 2.85V, in this way, the energy density of the battery has dropped by more than 10% compared with the conventional one; the second is that during the high-rate discharge period, severe heating occurs. When discharging at 20C, the temperature reaches about 70 degrees. Due to the phenomenon of iron ion dissolution at high temperature, it has an adverse effect on the cycle life and safety of the battery.

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