Method for making ferrous lithium phosphate/carbon compound material of high active disorderly ferric phosphate

Abstract

The present invention belongs to energy material, and in particular relates to a method of using high-activity disordered iron phosphate to prepare ferrous phosphate lithium / carbon composite material. A ferrous iron source is mixed with phosphorus source solution according to stoichiometric ratio, has hydrogen peroxide added in, has pH value controlled and is stirred so as to prepare high-activity disordered iron phosphate. iron phosphate, a lithium source and a carbon source are mixed pro rata, ball-milled uniformly, spray-dried and treated via high temperature under protective atmosphere, so as to obtain high specific capacity ferrous phosphate lithium / carbon composite material of which the average particle diameter is 200-500nm, 0.25C rate specific discharge capacity reaches 145-150mAh / g, 1C rate specific discharge capacity reaches 130-140mAh / g, and 5C rate specific discharge capacity reaches 105-110mAh / g. The method is low in cost and simple in process. Prepared material is good in electrochemical performance and especially excellent in rate performance, which is applicable to battery anode material of electric vehicles and other large-scale mobile devices.

Description

Technical field [0001] The invention belongs to the technical field of energy materials. In particular, it relates to a method for preparing lithium iron phosphate / carbon composite material with high activity disordered iron phosphate, which can be used as a positive electrode material of a lithium ion battery. Background technique [0002] Lithium-ion batteries are considered to be the most promising chemical power source due to their high working voltage, high energy density, long cycle life, low self-discharge, no memory effect, wide operating temperature range, and no pollution to the environment, etc., and are widely used In all corners of society, including mobile phones, cameras, laptops, electric bicycles, etc., are closely related to people's lives and are inseparable. At the same time, due to energy shortages, lithium-ion batteries are expected to partially or completely replace gasoline and become energy storage devices for electric vehicles. [0003] Cathode materials...

AI Technical Summary

Problems solved by technology

Triclinic nanoscale iron phosphate due to Fe 3+ / Fe 2+ The existence of / Fe redox pair has a high specific capacity as the negative electrode material of lithium-ion batteries; the trigonal iron phosphate has the most stable structure under normal pressure, and the metastable orthorhombic (Pnma) Iron phosphate transforms into this structure at 700 °C, which can be obtained by liquid-phase method or hydrothermal synthesis of precursors and high-temperature sintering. However, because the structure is too stable, only 1 ) and orthorhombic (space group Pbca) crystal system iron phosphate can be synthesized by hydrothermal method, because it can form hexagonal lithium ion channels, about 0.2Li / Fe can be reversibly deintercalated during charge and discharge, and the electric The chemical activity is higher than the ferric phosphate of the trigonal crystal system, but lower than that of the orthorhombic (space group Pnma) crystal system (0.6Li / Fe reversible deintercalation); the amorphous ferric phosphate can be synthesized by solution precipitation, and can Calcining at different temperatures to remove the water of crystallization to obtain pure amorphous iron phosphate, but the higher the treatment temperature, the worse the activity of iron phosphate. Obtaining amorphous ferric phosphate without crystal water should be processed at a lower temperature. At this time, the ferric phosphate activity obtained is lower than that of the orthorhombic (space group Pnma) crystal system, and higher than that of several other crystal systems. Iron phosphate

[0005] But LiFePO 4 It also has unavoidable disadvantages when used as a cathode material

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